57 is more than 53.
Lets see if I can explain this better.
I have a custom island on one ssite.
Called
Upcoming events
If I visit the control panel> custom islands
On the left side are numbers for each island.
Upcoming events is number 12.
When I save that island it creates a file in the cache folder called:
portal_box_40.php
So when you get a error it is reporting the actual file name that has the error
Due to what I tried to explain above in simple terms.
Because I am not savy enough to explain it in complex terms.
Thats just the way it is.