Why am I getting sometimes right

and sometimes unacceptable results from smartforms?

I want to display the items and at the end, the total of the items as a cumulative total, at the footer...

However I see that even though just 4 item is available from a kind, it comes 16 like:

item1 10kg

item2 20kg

item3 30kg

item4 40kg

item1 10kg

item2 20kg

item3 30kg

item4 40kg

it goes like that, for 4 entry, 16 entry comes and hence the total of kg changes...

Why is it happening?

Thanks.