make sure in the box that you have a 32GB if that's correct then my question is:
have you flashed any rom?
Device: LG G3 D855 32GB Black
Storage: Samsung 32GB micro SD Pro UHS-I Class 10
ROM: Stock version 10J
Recovery: Tethered TWRP 126.96.36.199
Samsung Galaxy S3 16GB White
Omega Rom v58 Stock Kernel