4% of £150 is about £6.
If they were trying to get VAT as well, it would be over £36 before fees are added on.
I have no idea what they’ve done, and you’ll probably struggle to find anyone at UPS who knows.
Packages are ping ponging back and forwards between the UK & EU countries all the time as mistakes are happening. The energy costs alone of that make me despair.
EDIT: oh, I see what you mean, VAT and duty charge on the value before the source country VAT was added, that is what they’ve doing, isn’t it. That’s right then. You need to pay UPS the amount they say, and then ask the shop/supplier to refund your the amount you paid them for VAT in their country. In future, do what Tom said.