Days Sales Outstanding to project future Accounts payable

Hey guys,

I just study a model and one thing I never get is how/why to forecast accounts payable.
In the model the formula for accounts payable is = (days payable outstanding / 365 * COGS)

I get what days payable outstanding means, it´s just the average number a customer takes to pay his invoice and shows the efficiency of the firm (correct me if I´m wrong).

But why do I take COGS as a multiplicator? Can someone here explain me that fast and simple?

Thank you guys