I've got MZMT installed and on the whole it works beautifully.

Occasionally though (with fairly light or zero weight items it mis-calculates and brings back the cost to be 71p.

All items should cost 60p packing plus at least the minimum amount of 23p (depending on the customers choice of shipping method).

Some of my items weight 0.003kg and the cart adds up the weight correctly but the shipping estimator disregards the total weight and works as if there were just one item.

I'm not losing sleep over this as it's only a few pence here and there but I am curious as to why it should be happening.

Any ideas?