Rail repairs

[sajm0n]

From manual:

Rail is repaired at a rate of 3 hexes per turn if the map supply level is 5 or higher.

What does 3 hexes per turn mean? 3 at any given line, 3 in the region, whole map?
What if map supply isnt 5 or higher, they arent repaired at all until it is?

[AlvaroSousa]

3 in a line assume the whole line is in 5+ map supply level.

[sajm0n]

So just to make sure i understand correctly, if my damaged rail line shows supply levels of 1-3-5-7-5-3-1, all 5 and 7 hexes are getting repaired and 1-3 ones wait until next turn?

Is there any way to tell which ones are getting repairs first if there are 4 hexes with 5+ supply to repair?