I've played a bit with changing recipe result.

recipe game
60 60
70 70

80 80
81 42
89 58
90 60
91 62
92 64
100 80
105 90
110 100
119 118

120 120
180 140
181 143

Seems that formula that splits items to stacks is messed, if there should be more than 2 stacks it subtracts instead of adding items, in multiples of (stacks - 1).

A "fix" for now is to put recipe at 105 items - it will produce 90.
But the recipe display will be wrong ...