In a column of type formula, the NB_ELEMENTS () function is used to display the number of elements contained in selected columns.
NB_ELEMENTS (Column1, Column2)
NB_ELEMENTS (Documents received)
I counted the number of items in the Received Document column to know the number.
NB_ELEMENTS (Received Documents, Subscription)
I counted the number of items in the Received Documents column + the number of items in the Subscriptions column to know the number of items in my client's file.
In the same way, I can count the number of elements linked to another table.
I counted the number of invoice statements from my Invoice column issued to a given customer.