iPod touch says memory is full even though it isn't

Ok so I tried to download a movie but after I started downloading it I noticed that it was going to take up 2.8 gb of space on a iPod touch with 8gb so I cancelled it but when I went to videos it was one there so I clicked it but then it just started streaming the movie over my Internet but when I went to usage on my iPod touch it said that I had 1.4 gb left and I had used 5.0 and I knew there was no way I used that much so I deleted that movie and it still said I have 1.4 gb avaliable I reset the iPod touch but did not restore it then I went to a website that convert mb to gb and I added up all the gbs in my usage area and it is really supposed to be 1.9 used not 5.0 I don't know what to do please help