http://www.simetric.co.uk/siprefix.htm

"Note: A very common mistake is that the prefix milli- stands for a millionth.
WRONG!!
As can be seen from the table above, milli stands for a thousandth. It comes from the French, mille for 1000 - they could not use it for the 1000 prefix as that was bagged by the Greek word, kilo"
Perfect :) Thanks!!! That links going to come in handy

So I just need to take 2 x 31.25 = 62.5 samples and somehow work out how much memory that takes up

62.5 X 16 = 1000kb I think

1 megabyte

Foook it that will do