It depends. It could be that it, a device, can store up to 1000 gigabytes, which is 1 terabyte. Also, it could be that a piece of software takes up that much space.
It is storage.1000 Gb is 1 Terra byte . some operating system utilities to delever report 931Gb or 953,674 MB. it qualify computer memory or storage memory . the GIGA BYTE is a multiple of units for digital information of storage .The usage of unit giga bytes continuous depends on the usage. It capacities usually means 100000 MB.
Probably its virus,this tipe of virus are created to bug your computer and make you need a formatting.
But if you found something like that in the internet just fotget.
