Have i ****ed up my UCAS? (pics to aid)

I dunno how to upload pictures it didnt work ? :/

Ok i was given an invitation by one of my offers to send a mini-project to see if i got an interview, and at the bottom of the page it said your reply, so i press accepted. I pressumed it meant im accepting doing the project and will send it. I'm not sure if this means i wont be able to accept other offers (but its not an offer just an invitation) when it comes to accepting my choices, but it says i can still cancel the offer. Anyone else done this?