Yoann, welcome to the forum. A little advice. Counting perorations does not do a whole lot of good - you need a perforation gauge. If you need one you can print one off the internet.
www.stampsmarter.com has one that is printable.
The red stamp that is "cut up" is normal - a large sheet of these were cut up into four panes of 100 at the printers. Hope this helps?
Peter