The goblin Emporium can not handle a non-integer reduction to the number of item needed.

for mexamples - after putting up 7 items i get - Requires -0.1374000000000004 more items to roll for a mystery item!

my Layla-Kobo combo get 3.1374 Less Item Needed for Goblin Emporium

Solution - round down when calaculating with layla for Goblin Emporium