All I can say is that the “sobremesa” has a great significance and importance in Spanish culture–food and animated conversations with friends and family over the dinner table are intertwined in their way of life. Spanish restauranteurs understand and accept this deeply rooted custom.
In restaurants in Spain, the waiters will leave you to yourselves after a meal and never bring the bill after your meal without being asked to do so. The exception to this—when a particular restaurant has adopted the new “two seatings for each meal service”, as I mentioned above at Castelados in the bar area and on the terrace.
In this case, the waiter will gently remind you that your time is up and that your table is reserved for the next diners.
Here’s another newspaper article about this unique custom-