I think that calculator is a little bit too optimistic...

All of the calculators are too optimistic - but I think it's the fault of how BURST and it's pools are structured more than anything, the pools appear to only report the size of the last machine that reported a deadline when someone (like me) has more than one machine mining to the same address.
I generally figure 30% less than what the pools estimate.
This is why I always tell people not to go by what the calculator tells them as it's only there for a guide on what could be earned mining from the amount of TB. I have never used the calculator yet and just go by the average we mine in a month which for us is around 3,000 to 7,000 Burst coins using 20TB. And we average around 1 block mined each week, some weeks it can be 2 blocks depending on how lucky we are as it all comes down to luck when mining any crypto currency.