What does the 'Levels' data include in the editor build log?

I have the following editor build size report in my editor log:

Textures      40.0 mb    33.9% 
Meshes        17.6 mb    15.0% 
Animations    0.2 kb     0.0% 
Sounds        9.4 mb     7.9% 
Shaders       68.9 kb    0.1% 
Other Assets  64.6 kb    0.1% 
Levels        46.2 mb    39.2% 
Scripts       124.0 kb   0.1% 
Included DLLs 4.1 mb     3.4% 
File headers  406.9 kb   0.3% 
Complete size 117.9 mb   100.0% 

What does the Levels include? I guess it's saving positions of the level assets. But why is it so big here? This is an iOS build. I assume it's either occlusion data (but this is only an uncompressed 1mb for each of my 3 levels).

It might be the 'Static batching' option? However, disabling this option does not reduce my build size (cache?).

This was caused by static batching. AFAIK this is the only main cause of extraordinary big levels. Normal sized levels are in the +/- 1mb range.

So, How to solve this any idea.