playoff with teams from multiple competitions

[Ilici Man]

I am trying to set up a league system where, after the regular season, a playoff/playout league is formed using teams from both the top league and teams from multiple series of the lower league. the final standings of this playoff league would decide which teams are promoted, relegated and staying in their previous division

I'm having trouble figuring out where to tie all the divisions to this league and how to decide which teams get to play in it. 

Right now I've tried to use just two divisions. I tried setting that 10 teams go from the top one and 6 from the lower one for a total of 16 but I can't even get this right since I'm getting this error

https://imagizer.imageshack.com/img924/3816/3JSrji.jpg

Edited November 13, 2023 by Ilici Man