Help! Simple maths not working?

Hi all - I'm really stuck and need some help. Warning = novice Access user here 🙂

I'm trying to add a calaculation to a query - when I try to multiple a field by a number I get a calculation that is nowhere near right eg. [field] * 52 - in my case I'm trying to calculate $400 x 52 ($400 a week as listed in my field by 52 weeks a year that I type in) and the answer I keep getting is $104. Any idea what is going wrong? Thanks sooooooooooooo much in advance!