This is another see me once, see me twice riddle that has been done by @Cashbee. Here is a link to the last one done by them.
See me once, I am a change,
See me twice, changes have already been made.
See me once, I am 4,
See me twice, I am 6 and 2.
See me once, I could be done here.
See me twice, people have done this here.
Hopefully this isn't too tricky. Thought of it on the way home last night and thought it could be interesting. Good Luck!