Some time ago I listened to a Rabbi talking on the radio about the meaning of food left over after a meal. Unfortunately I was not paying attention. I then saw a question that asked what the meaning was of the 12 baskets of food left over after the 'miracle of the loaves and fishes'. During the Rabbi's talk I had subconsciously made a connection between the two. Therefore, what is the spiritual meaning of a meal that has leftover food?
Refer to Kings II 2:43
In summary, there was a tremendous famine in much of Israel. Someone comes to Elisha the prophet, who was sitting with 100 prophets. The person brings 20 loaves of barley bread and some parched grain. Elisha says "feed this to the people". Elisha's servant mocks him and asks, "What? This is enough to feed all 100 people??"
Whereby Elisha says that G-d said that not only would it be enough, but there would be left-over. And, that's exactly what happened.
The Edot Hamizrach as well as other Sefardim include verse 44 at the end of the Grace after meals.
It seems that this verse may be one source of the notion that having left over food after the meal is a sign of a blessing from G-d. The concept, more importantly, I think is to realize that G-d Himself is the source of all food and sustenance and one should not lose faith in him to provide or behave as Elisha's servant did. He demonstrated his faith in G-d (and in Elisha, G-d's servant.)