
They are saying that interest on the sum of £2620.00 since 1st March this year amounts to £725.15.
Let's give them a few days benefit to keep the sums simple, and say the period is six months from 1st March 2023 to 1st September 2023.
If £725.15 is six months interest, then a whole year's interest is double that at £1450.30.
Just at a glance we can see that the annual interest rate is over 50%
Or to use detailed arithmetic...
1450.30 / 2620.00 x 100 = 55.35%

OK, we can also see in the Particulars that some parking incidents were back in 2017, but as the Claimant states in their Particulars of Claim, their calculation is 'at the rate of 8% p.a. from 01/03/23 to date'.