Gas gauge calibration unit

I have written some code for the calibration process.

The calibration process, with the help of the user, grabs the end points of sender resistance, and pwm drive, for empty and full tank. The points are stored in eeprom for the re-scale function. The eeprom stores the values, and does not require power.

The user interface consists of two buttons, one marked E, the other F, and a LED. The calibration will likely happen once, at empty tank for empty points, and again when filled.

The button pushes are as follows:
Press both buttons, about one second, the LED will blink, release. This is entry to cal mode. The E, F button clicks are used to change gauge reading to desired value. E moves towards E, F moves towards F. The resolution is about 0.5% per click, so it might take a few to notice a change. This is done slowly to give the gauge time to react. Bi-metal gauges are slow. If at empty, make gauge read empty, then press and hold E button to exit. Similar for full, do at full tank, except F button used for exit. In both cases, the final click is removed from adjustments. The LED stops blinking, and the gauge function follows sender. Re-calibration is only necessary again due to gauge drift, sender change, or an EMP that clears the eeprom and renders all modern cars dead on road.

I think this way is fairly good, but perhaps a more creative person can visualize a better way. Please help with comments.