Recorded macro for date format is different with the recording process

I macro record when I do this manually :
select a cell with a date value
custom format it to "d/mm/yyyy"
stop the macro.

The resulting code is :

Selection.NumberFormat = "d\/mm\/yyyy"

I thought the result would be:

Selection.NumberFormat = "d/mm/yyyy"

The other thing is when the manual custom format process is "dd-mm-yyyy",
the resulting code is :

Selection.NumberFormat = "d/mm/yyyy"

Maybe someone can explain it to me why the result is like that ?
Thank you in advanced.

My computer Short Date setting is : dd-MMM-yy