Steps to reproduce:
1. Select a sample in the samples pool.
2. Delete the contents of the fine tuning field.
3. Type the following value into the fine tuning field: -24
Result: The field now contains "+42"
This field is wonky in other ways as well, for example, selecting an existing value and pressing "Backspace" does nothing. Selecting the existing value and typing any numbers also does nothing, except for the number 0, which becomes inserted at the beginning of the existing number.
I just noticed that the reported behavior (field contains "+42") happens when the deleted existing value was negative. If the existing value was positive, then the resulting value of step 3 will be "+24").
