Tesco clothing mens wear discount

[Becx N Gav]

DH just spent about £50 on mens wear (online) as we already had a voucher and there is an offer on for 20% all mens wear, however when he checked out it took £20 off the total and we hadn't entered the voucher code yet! We were still able to use our voucher.

I guess this is a mistake and it should take off 20% not £20! Hope someone else can use this (sorry if it's been mentioned but I didn't see another thread)