DNG Specifications v1.7 and SDK

Hello,

I'm trying to understand the GainMap opcode from the DNG specifications v1.7. Seems that the source code provided by the SDK is not fully compliant, for example outside the gain map values should be replicated from the edge of the map and I can't find this behavior. The Black level is also subtracted before the gain function, and also this is not specified in the specifications. Is my understanding correct?

Thank you