What Big Files Not To Delete ?

[Kriscka]

Hi everybody,

I noticed that I've got around 18Gb of Big Files which some of them are called data.ext4.win00X (X being following numbers), system.ext4.win00X. Also I've got many files named XXXXXXX.nfv and XXXXXXX.nfa (X still being numbers) and one named B009995WKQ_ep6.aax.

Do you have an idea wether it's safe to delete them or if they're system files ?

Thanks in advance !