UNCHECK 'snap to grid' and it shouldn't modify the numbers

if it were me, i would do this:
1. i would hit reset
2. create my regions
3. make them all tiny and on the main screen (tiny == 300x400)
4. confirm the region names
5. set the PiP hotkeys

and THEN i would go one by one, starting with region4 and working backwards and set their positions and size.