you've probably a bad vendor incapable of reading an 11-year old RFC.
ifPhysAddress should be a string of bytes with the actual address in it (6 bytes for Ethernet-like media), and not a displayString with the ASCII representation thereof
You'll probably see the string is something like 30303a30303a31323a33343a35363a3738... 3a is a ':' character and '30' is 0x30 = '0'
The return value should have been the six octets: 0x00 0x00 0x12 0x34 0x56 0x78 which would get displayed as 00:00:12:34:56:78
I'd bet dollars to donuts their SNMP implementation for returning ifInOctets and ifOutOctets is similarly broken and wraps at unexpected times.