Difference between compilation size and size of the app

Hi, im tryying to reduce my app under 100MB , but i see that when i upload an app to itunes , in compilation info i see for example: 53.1 MB but if i go to the app store details page, the size is 63.9.
I hace more examples:

53.1 - 63.9
57 - 68.2
61.7 - 73.4

Always 20% more, why this? and what is the good mesure for the 100 OTA?

 

The update section of the reply by Vizlix in the thread below explains clearly the way to calculate the App Store size. Make sure you do the calculation on a copy of the .app.

http://stackoverflow.com/questions/30620322/xcode-6-3-estimated-apps-store-size