These are lottery numbers.
The location above is, as per Graham Greene's novel:
“…the square at the top of Lamparilla Street… swallowed up among the pimps and lottery sellers of the Havana noon.”
Unlike modern lotteries which are computerised (and often allow multiple 'winners' through duplication), the Cuban lottery took a form where sellers would buy specific numbers, and then re-sell them. Obviously, certain combinations were supposedly more valuable than others, particularly if they were a buyers lucky number. Furthermore, vendors would try and convince buyers that their numbers were lucky, by whatever means possible.
Green considered the lottery a blight on Cuba, and as per the extract below from his journals, considered the lottery to be profiteering from desperate superstition;
While the story was emerging I set about curing a little of my ignorance. I made Cuban friends, I took a car and traveled with a driver around the country. He was a superstitious man and my education began on the first day, when he ran over and killed a chicken. It was then he initiated me into the symbols of the lottery — we had killed a chicken, we must buy such and such a number. This was the substitute for hope in hopeless Cuba.