I am really sorry that you did not get an answer to this question – albeit I recall the question, and I thought I had answered!!
My interpretation is they will look at this in line with the way that you record your revenue into your books – if you do this on a cash basis, then it will be the cash revenue you have in the month prior compared to last year. If however, if you do your books on an invoice basis, then it will be the invoices out (including cash in and receivables).
hope that helps. Andy