You are allowed 1 ounce of finger or thumb weight, but a total of 3 ounces of topweight.
If it has 1 ounce of finger weight, and not more than 3 ounces topweight, it is legal.
You are allowed small imbalances in the ball. You are allowed:
1. One ounce of weight on any SIDE of the ball
2. Three ounces of weight on the top of the ball
3. You are allowed up to one ounce of either finger, or thumb, weight.
It helps to think of the ball as if it were a box. A box has four sides, a top, and a bottom.
It is not unusual to have one weight be OK, but have another be illegal. Such an occasion would be having a ball with three ounces topweight (which is ok), but also having over one ounce finger weight ( which is NOT ok ). In that case, the finger weight would have to be adjusted to within the one ounce mark.