As the others said call them and ask.
I was in a slightly different scenario where I was working and gave up work to go back to college. Hence, my salary was going to drop as I wouldn't be working. I was concerned as if it was based off the previous years salary I would not have been entitled to it. However, they explained to me that if there is a change in circumstances, e.g. no longer working, then this is taken in to consideration.
They may have averaged it out as others suggested, but if that was the case I'm not sure that I'd have got the full grant which I did. All documentation, etc.. was filled in correctly. But could have completely miss-understood the process.
Useful link on the whole grant situation: