Just discovered that I only partially understood the function, perhaps it is better! You can set more values comma-separated and this let you pick them quickly. But this way you cannot set a custom value without resetting the preset*

Instead if you preset a single value the overwrite is easy, just long press.

* #[2] I suppose changing the multi value preset is infrequent, so the long press is better spent on the realtime custom amount, while the first can be moved in a general preference section (after an initial setup, like now).