Questions about billing/cost, monthly caps, and VAT

I’m considering switching to DO as my VPN provider, but I’m having trouble working out the cost of a VPN for comparison purposes. For one thing, I’m confused by the concept of a “monthly cap”:

On this page, it says “All droplets are billed hourly, up until a monthly cap. We have estimated that each month has about 672 hours (28 days)”

But on this page it says “All droplets are billed hourly, up until a monthly cap. We have estimated that each month has about 720 hours (30 days)”

Which of these is correct? And in either case, what exactly does it mean when compared to a calendar month? Would I be invoiced every 28 days, every 30 days, or every calendar month? If the latter, does that mean I get a certain amount of free days depending on the length of the month? (I’m considering a scenario with one VPN running 24/7/365, using PayPal to prepay.)

My other question concerns VAT. As a UK resident, I’d expect to pay VAT at 20% for services, and for it to be charged at the point-of-sale. However, the Ts&cs say that “Subscribers are entirely responsible for the payment of all taxes.” How do EU customers normally deal with this? To my knowledge, there is no mechanism by which I can pay VAT to HMRC (the taxman) myself, I can only remit them VAT I’ve charged other people for my services (and even that, only if my business is large enough to be VAT registered, which it isn’t.)