Options for HEX2BIN utility ?

The help screen on the HEX2BIN utility does not give any hint to the usage of 'n'.

I want to convert a HEX file (less than 32k) to a binary file with size=32k (8000 Hex).
Unused bytes should be padded with FF.

I expected the following command to work:

HEX2BIN /P0xFF myfile.hex

but this cmd pads with 00.

To my surprise it works with this command:

HEX2BIN /L0x8000 myfile.hex

Can anyone explain?