Fan belts query

Friend has a Roma-home camper on a 1998 Piagio 1300 Pick up, the fan belt fitted is a Gates 6211mc x 9.5mm I think it should be a 6212mc x 10mm the 6211 seems very low in the pulleys but not bottoming.
Who is correct ?

Don't know if this helps at all - I just fitted e new one for my 2000 1.3 EFi Hijet. It was a Contitech rather than a Gates one - I just used Eurocarparts which told me what I wanted based on the Reg number. It came up with a 10 x 775 one. As far as I can see online the 6211mc seems to show as being 9.5 or 10 depending on what site you are on.

That said, after two weeks mine is already making a bit of noise again at start-up!