From the PC Map Selection PDF file:
"The above example shows several cells in the map selected. To do this, first click on the starting cell (in this case 5% throttle and 2,000 rpm). Then press and hold the “shift key” on the keyboard. At the same
time use the “arrow keys” on the keyboard to select multiple cells. The selected cells in the above example are in the typical cruise area of most bikes (some bikes may cruise at a higher rpm, more cells can be selected). You can now use the “page up” or “page down” keys (on the keyboard) to adjust all of the selected cells evenly. Pressing the “page down” key four times would lean out the selected area 4%.
You may wish to do this to improve fuel economy on long trips."
I'm not sure that this proves the numbers are percentages...though, each time I press "page-up" or " page-down" the map numbers change by one.