The easiest way to review which accounts are being included in your Accounts Receivable / Trade Debtors calculation is to navigate to:

Budgets & Cashflow > Cashflow Settings > Cashflow Forecast

The main screen shows the profile of how the Debtors balance is predicted to be received over the time periods.

The Advanced View at the top of the screen in the middle can be toggled on (green)

Then if you SORT BY and choose CASHFLOW TYPE, scroll down until you see the accounts that are coded as Debtor Days.