item random() (was Random(3) often returns 1)

[Geoff Canyon]

I just ran this code

on mouseUp
   repeat 1000
     add 1 to x[random(3)]
   end repeat
   put sum(x) into y
   combine x using cr and tab
   put x & cr & cr & y
end mouseUp

and got this:

1	329
2	328
3	328

985


Note that the three numbers don't add up to 1000, but there are no  
other numbers. ???

Running it again I get:

1	339
2	335
3	338

1012


_More_ than 1000? What the???

Even stranger, making this slight adjustment fixes it:

on mouseUp
   repeat 1000
     put random(3) into z
     add 1 to x[z]
   end repeat
   put sum(x) into y
   combine x using cr and tab
   put x & cr & cr & y
end mouseUp

Anyone know what I'm not seeing?

regards,

Geoff