Self Employed Maternity benefit query

Hello all, I have just gone on maternity leave. I am currently registered as self employed - been s/e since Oct 2009.

I got a letter from the maternity benefit office saying I would get 270 a week based on the relevant tax year 2008 (when i was employed and earning quite a bit).

However, the first payment has gone in and it is only 225...does anyone know why this is?? I was expecting the max payment but only getting the min payment....

Can anyone suggest why this might be or is it an error?

Perhaps your first payment is not for a full week. That payment may bring you up to the end of the SW week. Wait until next week's payment goes through and if it is not as stated in their letter contact them for an explanation