I haven't been doing this long, and I only have 116 characters. But I constantly get asked to review the characters for heat (re) and thank you (xie xie)? Why don't characters get repeated equally often? Is it because I missed out writing a hook (on Wacom)? Is it because they have a lot of strokes? What happens if I delete them from the learning queue?

Margaret

The reason that you see the characters at different rates would be because of the spaced repetition scheduling:
http://www.skritter.com/faq#scheduling

Are you sure that 热 and 谢谢 are being marked correct when you write them (with a green border)? You can use the correct button to toggle if not. Otherwise, there might be some more info here:
http://www.skritter.com/faq#frequent_repetitions

If you delete them, then they'll stop showing up. If they are added again (from another list, say), then you'll pick up where you left off on those words. That is, they'll probably be overdue, but Skritter will remember your progress on them. There's more info on removing words here:
http://www.skritter.com/faq#remove_words

Hope this helps!

And to put some of what Nick said into layman's terms if you don't know terms like SRS, etc: the less success you have with words (based on the way they're graded when you study them), the more often you'll see them. If you had a harder time with those words early on, then they'll show up more often than those that you had more early success with.

If you feel like the words are being graded improperly (i.e. you know it but it's marked as wrong, or you don't know it but managed to scrape by with a correct grade), you can and should adjust the grade for that item yourself. If the way your items are graded isn't in line with your actual knowledge, then it will mess up the scheduling system (the SRS algorithm).

Thanks very much. What I meant was that these two characters were repeated more often than any others, although I know them, that is, the spacing was unsatisfactory. I did not understand about the green border. Now I can see what is wrong. If I accidentally press the wrong tone, for example, or start writing a character in the wrong place, which is quite easy with this Wacom pen, it gets a pink border, but I can correct that myself if it was an accident. So I don't need to repeat them.
I realize about the SRS, but I can't be bothered to read up the details of the algorithm or whatever. When I originally learnt Chinese in 1969, I used to put record cards in a series of envelopes and the ones I didn't know got repeated every day, and the others gradually less frequently, but I think the Skritter system is more subtle and it seems to work well - except that I must have kept doing something wrong with these characters.

Thanks for the explanation. I did look at the FAQ, but I didn't find the details of how the fields work or realize that I could change the colour around the character.

Margaret