I still don't understand why ci can mean both us and it (and there). Wouldn't "it" be la or lo? Is it because it's an indirect pronoun? Don't even get me started on "ne".
For people who read this in the future, it's probably because the courses for english speakers typically use standard american english.
Aside from what DL accepts, since 'Ci penso io' means 'I'll take care of it', in this third person plural subjunctive whatever the hell tense it is, could this also mean
...if they took care of it
"ci" means "us" as object and indirect object. "ci" can mean "at it" or "about it" "ci penso io" = I'll take care of it / I think about it. "ci" can mean "there" non c'è nessuno" "nobody is there". Better learn some standard sentences with the different meanings. As you see everything depends on the context.