In-band vs out-of-band management on PTP820G

What is the difference between in-band and out-of-band management service? And how switch between these types of service on PTP820G?
The problem is that I cant create any radio interface Type SNP, s-tag, because of critical error.

In the written explanation there is the management service with number 257. In my default configuration of PTP820G this management service has number 1025. And I cant do anything with it, for example, delete it. Please, explain the difference between in-band and out-of-band management service, and how to switch betwween them.I havent found any solution in the Users Guide, and switching between in-band and out-of-band isnt even mentioned there.