I think in that case the FMS would give an error if you tried to enter 170 for the the cruise altitude, however it should accept 17000.

 

FMC accepts both full format and three digit format most of the time. Its not like you would want to set up cruise altitude under 410ft anyway - so it will know that if you put in a three digit number, it means this many times 100ft.

yea you can enter 170 or 17000 doesnt matter which format u choose its still the same 17000 in the fmc