TagA and TagB are just the two bytes (first and second) of the record header, nothing fancier than that. You don't need to decode them, DBCC Page does it for you, it contains info lik "Record Type = PRIMARY_RECORD Record Attributes = NULL_BITMAP VARIABLE_COLUMNS"

The "00000000" is the offset, so byte 0 = offset 00000000, so the first byte of the dump, in this case, Byte 0 is 0x30. The record has a null bitmap and variable length columns (but I didn't need to decode the header for that, DBCC PAge did it for me "Record Attributes = NULL_BITMAP VARIABLE_COLUMNS"