SA108 form and PRR correct completion?

I have an initial gross CGT gain of £3,249 and a Private Residence Relief of £303 making my net gain £2,946 which is tax free due to my CGT allowance. This also came up as a £0 CGT liability when submitting to HMRC within 60 days of sale. I submitted my end of year return with the following in SA108: Box 6 £3,249 Box 8 PRR Box 9 £3,249 Box 51 £-303 Box 52.1 £2,946 I have also included my capital gain tax return reference number in box 54 as well as the item 8 claim of £-303 as well as another sheet on the calculations to support. The issue I have is that HMRC have assessed me as having a £303 amount due which doesn't factor in the PRR. I want to do an adjustment, have i completed the form incorrectly?

Hi ,
 

Box 5 is allowable costs.  Your PPR deductions should be included in this value, so that box 6 (gains in the year before losses) would be nil (box 4 minus box 5 = box 6).  As there is no tax payable, boxes 52.1 to 52.5 would be blank . Thank you .