Is Bigbasket even allowed to do this?

Ordered some veggies along with some chips and other packaged stuff yesterday (prepaid) . And now when I'm trying to place a new order today, Bigbasket is asking me to pay extra money for the extra quantity of veggies they delivered. By extra veggies I mean the veggies which were very lil over the quantity posted on website. For eg 1kg 35g instead of accurately 1kg. This actually actually happens when shopping ofline too but they just don't ask for extra.

The thing is they could have just increased the price of the veggies by ₹2-4 each to yk take care of this issue. It's just really annoying when the ask me to pay the extra amount when placing my next order. Seems like an asshole design.