In the SOPL, for the period from 1 July 2007 to 31 March 2008 (9 months) you take 9/12 x 25920. For the period 1 April to 30 June 2008 (3 months) you take 3/12 x 28800.
In the SOFP, the prepayment is the period from 1 July 2008 to 31 March 2009 (9 months) and is therefore 9/12 x 28800