Instant App Quick Deploy

Hi there, I'm developing an Instant App version of a game. I upload it on Google Play and it works, however the download it too slow, due to the size of apk. So I decided to use the Quick Deploy, I created the AssetsBundle and uploaded it on a server. My Instant App now is made up by the loading scene w$$anonymous$$ch downloads the bundle from internet. However the size of the apk is larger than 14MB although there is only the loading scene and 2 compressed sprites. Why?

Thanks so much