Too many disk in the list

Mac Beginner

New Member

I have just received an hold macbookpro (2013). I have to re-install the OS but before, by listing the disks via the diskutility from the recovery partition, I receive a list with strange entries (printscreen). How is it possible to have so many disks somes with very low size (ie: disk 9 with 1MB) ?
Many thanks for the link, I'll apply the "procedure" but I'm still asking me how is it possible to have a list of disk ... The previous user did something "wrong" with many installations or ... ?