q half life kaplan kit

hello sir
i have a doubt
for calculation of corporation tax repayment
we calculate ctl on original ttp and ctl on revised ttp and take the difference bwtween both
but in this question.
4 years are there .. they have found out the corp tax repayment by the ablove method for years 2 and 3
but for year 1…
what they have done is.
they have multiplied 20 percent on the loss relief available to them
and that 20 percent of loss relief available to them is considered as the corp tax repayment..

why have they done like that?
shouldnt the original ttp*20/100– – revised ttp *20/100 be the corp tax repayment?
now the year 1 .. for them the loss relief available to them is restricted by 9 months..is it because of that
the question is called half life from kaplan kit

Corporation tax repayments  Year ended 31 March 2014   Corporation tax of £34,830 (£174,150 at 20%) will be repaid in respect of the  year ended 31 March 2014.    

Year ended 31 March 2015  
Taxable total profits for the year ended 31 March 2015 were originally £78,600  (£79,600 – £1,000 QCD relief) 
Taxable total profits after loss relief is £0  Corporation tax of £15,720 (£78,600 at 20%) will be repaid.
  Year ended 31 March 2016  Taxable total profits for the year ended 31 March 2016 were originally £50,300  Taxable total profits after loss relief is £0  Corporation tax of £10,060 (£50,300 at 20%) will be repaid.