That sounds about right Benhamine - you basically want to excercise along the full range of movement from full extension to full flexion. While doing negs though just concentrate on getting the form in, try to do them as slow as possible, and get used to the movement. My hands were very painful from the grip at first, but this week I was able to do normal pulls at least for 5 sets of 1, then I had to go back to negs.
Also, well done on 22 rounds! Sticking at it is the key - and ending on a note where you don't feel acutely painful (e.g. sharp / stabbing) but pretty much unable to do anymore is perfect! More than that and you've probably done yourself a little injury and your recovery time might be a week or more, less than that and you are not hitting your potential.