Oracle algorithm for probability of item drops

3f:4779:

when execution reaches here, hl has been set to a specific value (483d for digging). Points to some kind of probability table?

call 041A ; get random number in A
and a,3f
call 0205
jr z,47ae ; if zero flag is set, no item appears
...

00:0205:

push hl
push bc
call 0223
and (hl) ; this instruction will set or unset the zero flag
pop bc
pop hl
ret

00:0223:

ld b,a
and a,f8
rlca
swap a
ld c,a
ld a,b
ld b,00
add hl,bc
and a,07
ld bc,00f8
add c
ld c,a
ld a,(bc)
ret