Energy Bills Support Scheme discount and direct deductions

I came across a client whose electricity bill is paid by Direct Deductions from her Universal Credit, plus deductions for arrears.  British Gas has received the £400 discount and has used it to take £400 off her arrears.  As the money they are entitled to take for ongoing charges can be increased through their estimate of her average fuel costs, her total deductions from her UC (average ongoing costs plus 5% personal allowance against arrears)  will go up but she will be as cold as ever!

I think this must be wrong.  In effect they are taking more than they have agreed with her (5% of personal allowance) against the payment off of her arrears. The scheme states it is specifically to reduce energy bills, so I think it should be a £66 for those 6 months set against the increase she will have for deductions for her average fuel costs.

For people on pre-payment meters (who are often also in arrears and have the meter set to recover) this problem is addressed - they are receiving monthly vouchers, which they can use, so the rate of deduction to recover their arrears remains the same.

Has anyone come across this?  Any comments?