Ok, i was trying to figured it out, i normally don't use checkbox.

Checkbox1 - OnCheck
Spoiler (Highlight to read)
Set(
varCheckbox,
ThisItem.Value
);
Set(
varSelected,
(LookUp(
results,
(Title = varCheckbox)
))
)
Set(varCheckbox,ThisItem.Value);Set(varSelected,(LookUp(results,(Title = varCheckbox))))
Checkbox1 - OnUncheck
Set(varCheckbox, "")
labelShowLeftHours - text
Text(varSelected.Title &": "& varSelected.'Choice 2'.Value &" hours left")
I get from list A (name Checklist) the option for the checkbox in the gallery.
List B (name results) is like that

So, this was just an example, hope it helps.
Francesco