Go to where John first enters the Nakatomi building to attend the Christmas party. The desk clerk tells him to type in the name of the person he's visiting. The screen spells Gennerro wrong at first, then when he clicks on the name it miraculously changes to the correct spelling. Watch carefully!
I find it mildly amusing that you spelled the name wrong here. I haven't checked the movie, but I would not be at all surprised if it were to be spelled correctly and you spelled it wrong here. It is 'Gennaro' as opposed to 'Gennerro'.
If I remember right, he doesn't type the name at all. Instead he chooses which letter it starts with and then chooses it from a list. Because he doesn't type his own name in when he finds out that she isn't using his name. He just hits the m or the g in either case.
The mistake is actually when he touches the "G" list on the display Holly's name is listed with an a (Gennaro). Then when he selects it and it shows him that the office is on the 30th floor it's listed with an e (Gennero).