If payables increase then it means you are paying less to the supplier.
Suppose at the start of the year you owed 1,000, and you buy goods for 5,000. That means you now owe 6,000. Suppose you don’t pay it all and end up owing 4,000 at the end of the year. That means that you must have only actually paid 2,000.
The 2,000 is the purchases of 5,000 less the increase in the payables of 3,000.