Is there a pattern for paying parking lots?

Last Friday, I was still in my wife’s lab at 19.45. It’s on the 4th floor of the Liege Hospital. From there, I could see the parking lots (for visitors).

general view of parking lots

more precise view of parking lots

Far away, the free parking lots were congested, as usual. But I was more interested in the paying parking lots, the ones that are the nearest from the hospital. Despite the fact that it was 19.45, there were still some cars. Some cars were there since the morning or the afternoon but some of them were just parked there a few minutes ago. I tried to draw where the cars were.

paying parking pattern, clic to enlarge the plot

Exits (to the hospital) are below, left and right (in the diagram). Visibly, people parked their cars near these exits. Were they there since the morning? One hypothesis is that they came very early in the morning and that they are still in the hospital. Or they just came after 18.00 and these lots were free. It could be interesting to study how visitors are using these parking lots. I am wondering if one could find a pattern for this paying parking lot (and I am also wondering if it there would be a practical interest in knowing that).