Uc appeal backdating help

So, the person i care for was recieving LCW ESA. He moved area so had to then claim UC instead, so they then awarded him UC LCW rate as soon as his UC claim started as expected, without any waiting period to get the LCW money.

Then fast forward a bit and i knew he was entitled to the LCWRA UC after reading all the rules ect, so i submited an appeal on his behalf to challange the LCW decision and to recieve LCWRA from the start of his UC claim, instead of LCW.

The appeal was successful and ruled in his favour. So now they have come round to sorting out the backdated money, i was expecting the LCWRA rate would be backdated to the start of his UC claim because he didnt have a waiting period or have to send dr notes ect and was getting the LCW extra money too from the start. But what they have done is, gone through all of his previous payment statements and put the LCWRA extra money/element ONLY on the dates starting from the 4th month of the claim, so they have not awarded it for the first 3 months of the UC claim.

And on top of that, they have actually removed the LCW extra money too from the first 3 months of statements, so his payment statements state that he was getting £130ish less those months than what he actually recieved.

So then based on that, they have worked out they only owe him £600 backdated for 5 months of LCWRA extra, it would of been £900 but because they removed the LCW from the first 3 months it removed over £300 from the backpaid amount. The total amount we expected was approx £1700, which would of been the case if they had awarded the LCWRA rate from the start of the claim. Please advise?