Welcome to Android Central! What phone do you have? So before you tried to download the app, you had how much internal storage available? You said "out in gig," so I can't quite decipher that typo or autocorrect. Do you only have one partition of Internal Storage, or are there two partitions, like an "App Storage" partition and a separate "Internal Storage" partition? If that's the case, then perhaps the App Storage partition was already that low to begin with, and the space you thought you had was on the separate Internal Storage partition. See this guide for more info:
http://forums.androidcentral.com/amb...-warnings.html