Should be only having an impact when you try to trigger on that group. For just assigning incoming values to the item it should not have an impact.
Yes, those .map files belong to the /transform folder. AND you need to install the map transformation service!
Here is a nice explanation:
I would recommend using a Switch (ON/OFF) or Contact (OPEN/CLOSED) item and replacing your Number item with one of that options (and using mapping to convert the numbers to the states a switch or contact item is able to understand).