DD said to me this afternoon "I am 4. And Smillie (her imaginary cat) is 10. So Smillie is 6 years older than me." Then this evening she had computer time. We use a timer, which should be set to 20 minutes, but it was only on 15 minutes. So DS protested on behalf of DD that she only got 15 minutes, not 20. So DD says "I should have 5 minutes more."
So, it is obvious that she can add and subtract in her head. But at the same time, she also likes to do math worksheets, which she gets at pre-k on rare occasions, or she asks me to make some for her. I make really simple stuff like 7 + 2 = and 3 + 3 = ... She makes this whole production of holding up 7 fingers, and then 2 more fingers, or asking me to hold up the other 2 fingers, and then counting them all out individually 1-2-3-4-5-6-7-8-9, and then writing the number down.
If this is just a way she is having fun, "pretending" to be in school, then I want to let it slide. I also think if it is a stage then I'd also rather just let her be, and go through it naturally. Or maybe doing math in your head is easier than seeing the numbers and writing them, so she really does have to count them out when they are written? (Though I am doubtful here, she has been writing for a long time, she wrote her first "book" a year ago.) But if this is a bad habit, so she can be just like her peers, then I'd like to address it; though I am not sure how. Maybe some of you with older kids will have some insight.