Beersmith BoilOff/PreBoil Gravity


Hello Everyone,
I have a problem understanding the numbers in the "Boil Off Tool" of BeerSmith.
The attached image shows the following data:
 Starting Volume: 25.20 liters
 Starting Gravity: 1.053 (53 gravity points)
 Post Boil Volume: 21.98 liters
So far so good. With these information I am able to calculate the "Post Boil Gravity" on my own using the following formula:
V1 * GP1 = V2 * GP2 (1)
This gives me a post boil gravity of 25.20*53/21.98 = 60,7 => 1.061 as shown in the tool.
But the actual starting volume after subtracting the shrinkage due to the temperature difference is only 24.28 liters. Formula (1) needs volume data to be at the same temperature I assume. Therefore, I get the following result:
24.28*53/21.98 = 58,5 => 1.059
Why does Beersmith not take the shrinkage into account to calculate the post boil gravity?
