Kevin
@Vinicius.
It should be the previous season finishing positions for the top 14 teams and then the two promoted teams 15th & 16th but it doesn't always seem to work this way.
There is a known bug which often means the previous season champion gets low car numbers instead of #1 & #2, also second place is sometimes towards the bottom of the listing for the start of the season.
I don't know how important it is to fix this bug, personally I'd prefer the developers to work on the weather forecast and level of water on the track just before qualifying.
I agree with you, this question is not important, I was just curious ....