Hi again,

Explanation from the mobile How to play - FAQ:
How does the game progress offline and what are offline ticks?
        TL;DR: Higher "Max offline ticks" setting = more accurate offline progress but more time spent to calculate after opening the app.
        Every time the app is opened the game calculates the time spent offline and divides it into several chunks called offline ticks, with every tick being at least 50ms long (meaning that if you only spend 5 seconds offline, you will only get 100 offline ticks). Every tick will give the player production equal to the tick's length followed by the player's autobuyers buying if they can, repeated until all of the offline progress is simulated.
        The maximum amount of offline ticks can be increased in the Options from 1000 (which is the default value) up to 1 million ticks. Doing so will make autobuyers buy more often when offline, making the offline progress closer to online progress, up to 14 hours of accurate progress with 1M ticks in contrast to 50 seconds of accuracy with 1000, with the drawback being having to wait longer after opening the app to finish the simulation.
        When you press "Speed up" during the offline simulation the remaining progress is simulated with at most 1000 ticks.

Explanation from my old reddit comment (made before the "Max offline ticks" option was added):
From the pins in discord: "Every time you open the app, it simulates the offline progress with at most 1000 ticks, same as in the web version."
What this means is that when you open the app, it calculates how long have you been away and simulates at most 1000 game ticks.  If you open the app for example after 1000 hours, each of those game ticks is 1 hour long. So you get 1 hour of production, then autobuyers buy if they can, then you get 1 hour of production, then autobuyers buy if they can, ... and so on 1000 times like this.
And since autobuyers buy max 1000 times when offline, then you can't get as much IP/min offline as online. There is a 1000 IP infinity upgrade that gives you 50% of your best IP/min without using M, which was added to mobile because of this issue.
Most of the loading time when starting the app comes from simulating the 1000 ticks, so we can't increase that number without also increasing the loading times, which we don't want.
I hope it's clear

Explanation by one of the web-devs:
When offline simulation is active without the speedup, it attempts to run through your entire offline time as if you were online, which means calculating everything in steps of 50 ms.  The calculations in the game are intensive enough that running a lot of ticks can be very slow, which means simulating 10 hours offline might still take 15+ minutes.  By speeding up offline time, you force the game to simulate everything in 1000 ticks.  This gives you most of the production in most cases, but this also means that, for example, autobuyers will only buy at most 1000 times while offline.

When we added the "Max offline ticks" option we quickly discovered that some players with slower devices who set the option to 1M had to wait more than 30 minutes for the simulation. Sometimes you just can't or don't want to wait that long - that's why we added the "Speed up" option. It simulates the rest of the not-simulated offline progress in 1000 ticks, so the production that depends on autobuyers is not accurate, but it's fast.

If you don't press "Speed up" the offline progress is simulated accurately up to 14 hours with 1M ticks.

If you press "Speed up" the offline progress is simulated in the same way as if you had "Max offline ticks" set to 1000 - your autobuyers trigger only at most 1000 times so the production that depends on autobuyers is not accurate (1000 ticks means at most 50 seconds of accuracy).

The progress that doesn't depend on autobuyers (like some upgrades with passive IP/EP gain, the Replicanti gain, and the DT gain) is always accurate, no matter how much "Max offline ticks" you have or if you press "Speed up".

If you have any additional issues/questions please let me know.

Kind regards