Allow for negative values in Emitter Incdex

[armandobastos]

Hi, recently i had to log a drip tape in the Database, but it has a different behaviour compared to other tapes, as its flow decreases as pressure rises (see image attachment).

The field only allow ZERO or positive numbers, and this limitation is blocking me from proceeding with this project.
Is there a way to allow for negative indexes?

Thank you in advance.
I'm available if further clarifications are needed.