Cels Forum

">>circles around cel numbers in _sketches_ indicate a key cel

                  Err....where did you find this out!? I got curious - I had to go look 
                  at my cels, and several of the sketches have the number circled, even the 
                  cels aren't labeled 1 or end."

Of course ^^!
Because 1 cels and end cels are not the only key cels there
are - I really did go on at sickening length about this at my website
(URL posted before)

"Then again, a couple of the 1 and end cels I have 
                  don't have the number circled on the sketch!"

as far as I recall, all the sketches I looked at which I own
have the 1 or the end cel's number circled, so I don't know 
why yours may not - perhaps because it is obvious those are
key numbers, hence someone figured they don't need to bother
circling them ...?
That is just a guess :)