On the altitude and speed indicator for the helicopters, the number 6 will show up as the number 8. For example 165 will look like 185. This is also present on the map view and the mobile gps view(ctrl+m). The air station Mike-26 has it's name show up as Mike-28 even though one of the NPCs says 26 in the helicopter showcase.

EDIT: On closer inspection, 6 appears very similar to the number 8 but is smaller. This is probably because my resolution is 1024x768. Sorry for the inconvenience. {F19124}