In HTML you can set a min and max attribute for the input tag when the type is number. It’d be nice if Anvil exposed those…might be worth a feature request. Then you could set a min of 1 and be ensured you’d have no negative numbers.
With Anvil as is, you might look at the Anvil Augments dependency which allows adding non-standard events to components. Then you could have a key press event. AnvilAugment: Hover, Focus, Key Bindings Dependency