If I have data which is in the form of a count - in this case number of words recalled under two different conditions - is this nominal, ordinal or interval data?

There is a total of 50 words which could be recalled so the data range is 0-50. I thought this was ratio data but my tutor says as it is a simple count it is nominal and I have to convert it to a percentage before running parametric tests. I don't understand why this is the case.

Can anyone help?