The calculations are there.
Juice is the amount that insurance pays over the EV0 amount. If EV0 insurance would pay $5, then if you pay $5,50 for it there is $0,50 juice. The one who gives the insurance makes profits from the juice.
In the example there is an all-in on the turn, 100bb stacks and hero has 85% equity.
Let's repeat the situation 100 times and hero wins 85 of those.
Without the insurance
85 times hero wins pot of 200,5bb = 17042,5bb
15 times hero loses 100bb stack = -1500bb
After 100 repetitions hero has 15542,5bb
With insurance
85 times hero wins pot of 200,5bb, but pays insurance of 17,7bb = 15538bb
15 times hero loses but keeps his stack = 0bb
After 100 repetitions hero has 15538bb.
Difference is about 0,05bb per hand. If the insurance cost is 1c lower, it would be the same difference but benefits the player. So it's uite understandable that it's rounded up.
I can't explain it any clearer. Insurance is EV0 so it doesn't affect your winnings directly in the long run.
What was strange yesterday, I had 60% equity and it allowed me to use insurance. So maybe it has changed or there was some bug in the software (as it should allow it only when you are at least 67% favorite).