B80750 is indeed mov ax, 0x5007. Nothing wrong there.
Anyway the given code fragment should assemble into something like this:
00000000 B80400 mov ax,0x4
00000003 50 push ax
00000004 B80700 mov ax,0x7
00000007 6A09 push byte +0x9
If you assembled the .com file yourself you are doing it wrong.