[FMX]duplicateMovieClip help

Hey, my first post
Firstly this is one amazing website, best collection of tutorials ive seen for a long time.

Back to my plea
Here is what I have so far on a button, mc_day is the name of the clip to be duplicated and .num the var for a text field:

on (release) {
for (i=1; i<=20; i++) {
//duplicate last clip give unique name with i
duplicateMovieClip(“/mc_day”; add (i-1),“mc_day”; add i, i);
//relative path to text field
mcname = “this._parent.mc_day” add i add “.num”
//set text field value
set(mcname,i);
//Grab current x pos
size = getProperty(“/mc_day” add (i-1), _x)+25;
//Move duplicated clip +25 foward
setProperty(“/mc_day” add i, _x, size);
}

}

Now this failed to work until I added the ‘/’ infront of mc_day. Why are they required and what do they refer to?

I want this all contained within another mc so I can mask it and apply general settings to the whole thing like movement/alpha etc.
But on converting this to a mc the code failed to work even though the it is coded ‘relativley’, i assumed it had something todo with the ‘/’

Any input regarding improving the code or info on the slash would be much apperciated thx