==_root.ta._droptarget.length-3

I asked a question earlier how to count if the droptarget was the right one. It is a problem because droptarget is in a loaded film.

I got this answer:

if (_root.ta._droptarget.indexOf("/oa")==_root.ta._droptarget.length-3) r++;

It functions on my first droptarget, but not on the other ones. ex:

if (_root.t2a._droptarget.indexOf("/o2a")==_root.t2a._droptarget.length-3) r++;

What does length-3 means. I have tried to find tutorials about this but can´t find any.

Greatful if I get an answer //ditti