That documentation is not updated very frequently. It is missing some services. There are also NODE_BLOOM (0x02) and NODE_WITNESS (0x03) service bits.
Are these the only two?
And where can I read more about them to know what they indicate?
I'm pretty sure these are the only other two service bits in use. However it is possible that other software implementations are using service bits but not informing the rest of the development community that they are.
Generally the service bits have an associated BIP, but you will have to read through all BIPs in order to find most defined service bits; they are not so state obviously in the BIP title.. Even so, some developers like the developers of Bitcoin Unlimited do not participate in the BIP process so they may be using service bits that no one else knows about.