Looks fine from here. I would have preferred somehow getting it on the inside of the spine, since that part of the clip receives the least friction. If you do sign it there, find a way if possible to protect/coat the signature and number so they don't wear off. Also, most artists when numbering a piece as part of a series will use a slash rather than a dash as in "3/20", but that's as much as personal choice as anything else. Sometimes the first number is written like a superscript and the second like a subscript.