wifi data usage

[A65spitifire]

Hi i am using a netgear aircard 790s 4g on a brand new service i started this week ,and what i have noticed is that if i download say a 150mb mp4 file it will show up my data usage in real time on the aircard manager telstra page as using over 200 mb , when i called Telstra  to ask why this is i was given answers in very poor English that i could not understand , i would love a written answer as to why this is when the internet says  expect maybe a few MB more for packet loss ect  , but not over 50 Mb per download other wise i will soon be out of dats 

[ProfessorPhone]

Are you sure you are not reading it, including uploads?

[A65spitifire]

i am reading it as it reads on my usage page , as far as i am aware there is no uploads involved in getting the file .