You cannot connect this directly.
The "Zoomlevel" is the resolution you can download from the sources.
The compilation Level from Geoconvert is the definition of the output.
You can download Zoomlevel 7 and compile with "Level" 15. Does not make sense, but you can.
And in FSET the Level goes into negative to get more detail.
So Image Detail "Zoomlevel" Aeroscenery to FSET "Download Resolution"
you can compare like this; (approx…)
20 -> -2
19 -> -1
18 -> 0
17 -> 1
16 -> 2
15 -> 3
and so on.
What tile level you compile from your sources depends on what you want.
I would always try to work with the detailed download sources I can get. In this case for example the imprints of google maps are getting very small or even not visible, if you convert Image Detail "20" to only Level 9 to 13.