Well, if you have rented from that shop before, then yeah, you'd know what you're in for.Don't babble. I have machines rented from that shop, l know what I get and how to deal with. "Base IP amount" means the number of IPv4 addresses included by default, and one can usually add more of them when ordering, for about 3$ per address per month.
It seems that "they mean ethernet cards" was one of those quick-shots of Yours, just like "one cannot dynamically rewrite firewall rules", which do usually miss with me. You might consider to instead just ask me friendly how I'm doing things - because usually I know what I am doing, and the fact that people rarely do such things (outside of Russia, of course) doesn't mean they do not work.
But I would not put it past a US-based shop to be either sneaky or disorganized or both when renting cheap used servers on secondary or even tertiary markets.