Cooling Loss irregularity

I've been playing around with a calculator I'm working on, and I was looking at BS2 build40's cooling loss calculations

It appears that BS2 is doing one thing, but showing the other.

To illustrate, I'll duplicate the "Porter" recipe in BS2 Examples and play with that.

(PS: I'm in Metric)

...

If you open it up and switch to the Water Volumes pane you can see

Post Boil Vol = 26.58L
Cooling Loss = 1.06L
Pct Cool Loss = 4.00%
Trub Loss = 2.56L


Batch Size = 23L

So, 26.58 * 4% = 1.06, okay, fine

So, Post Boil Vol - Cooling Loss - Trub Loss should equal Batch Size

26.58 - 1.06 - 2.56 = 22.96, not 23

alternatively

Batchsize + Trub Loss + Cooling Loss = 26.62, not 26.58


It appears the Post Boil Vol is actually calculated as


(Batchsize - Top Up Water + Trub Loss) * 104%

ie

25.56 * 1.04 = 26.5824

which would mean a cooling loss of 1.0224

...

Now, I'm not sure which calculation is correct, but I do know that its confusing that BS2 seems to be using 1.0224 and showing 1.06

Perhaps the cooling loss should actually be calculated as :

Post Boil Vol * (1-1/1.04)

?

Or am I missing something?

Thankyou