mini PCI serial board support by RouterOS

I have a RouterBoard 532A with the 564 daughter card. I need more serial ports on my board set. There are a number of mini PCI serial expansion cards available, usually with 2 or more ports. The RouterOS documentation indicates that they only support com1 and com2. If I buy one of these serial cards with 4 ports, I only get one additional port? Is that true.

Walt