In the USA, when you visit a grocery store to buy fruit or vegetables or anything that needs to be weighed to determine how much you will pay for it, you place all those items in your basket and head to the cashier. The cashier then scans the barcodes on all the items and weighs the items that need to be weighed, helps bag the items, collects the amount owed, and then sends you off on your way.
Apparently in China, for items that need to be weighed, you collect those items as you would in the USA but then need to find the employee working the area. It’s that employee’s job to keep the area tidy and full of goods and also to weigh the items you’re purchasing and affix a label to the bag of goods for the cashier to then scan when you’re ready to check out.
It’s also a good idea to have a few canvas bag with you when shopping unless you want to pay 1/10rmb for a plastic one.