Skript "lambda" error?

# Code:

set {survey::%{_SID}%::total-votes} to 0
set {survey::%{_SID}%::votes::%loop-value%} to 0
slot {_start} of {_P}'s current inventory to stone named "&7%{survey::%{_SID}%::opt-%loop-value%}%" with lore "&bClick to submit" to close then run [add 1 to {survey::%{_SID}%::total-votes}]->[add 1 to {survey::%{_SID}%::votes::%loop-value%}]

# Error:

[add 1 to {survey::%{_SID}%::votes::%loop-value%}] is not a valid lambda statement

# All variables are set... i'm not sure what's causing this!