- open up the shop menu (using b) and select any item in the shop that you have in your inventory
- click sell amount and enter any amount higher than the amount the shop can buy (ie: 50000-stock+1 or higher), it doesn't matter if you don't have enough of the item
- click ok and it append the amount it could buy, even if we had less than the amount.
it should replace the amount with the amount it could buy only if we had more than the amount otherwise it should replace it with the amount we have.