I'm trying to understand a little machine code.

I have a HEX file that reads

80EFFEF0...

The disassembly shows that is equivalent to

GOTO 0x1fd00 - opcode EF80
(next line) F0FE

I understand a little about the reversed order of the bytes, so if I can
see how "80EF" is actually 0xEF80, but I get stuck when I get to how
the 0x1fd00 gets encoded into the HEX equivalent.

Can someone tell me how to figure this out?