The section maximum and minimum checkboxes have states set on them to make the count input visible when checked, but currently the inputs are visible at all times.
I've upgraded to 10.4 recently and as a result the inputs are actually always hidden for me. This doesn't seem to be the case on a fresh 10.4 install so that's a me problem, but this will fix the intended functionality along with my issue.
Configure a section and set the "Limit by" field to either "Region" or "Section". The minimum and maximum inputs should be visible below their relevant checkboxes even when they aren't checked.
Update the input name in the processSettingsForm callback, currently the path starts with layout_builder_limit but the correct start of the path seems to be layout_settings.
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Bear with me, trying to figure out how to do all of this for the first time :) Trying to set up a merge request.
Here's a patch as well. I think I've managed to figure things out... let me know if I need to do anything different!