You can always see the latest update along with the previous versions here:

https://github.com/spectrecoin/spectre/releases

You can make a calculation formula for staking, very simple with these considerations:
You get 2.20 XSPEC together every time, that is, you do not get 1 and then again 1 ...
Another data is 5% annual interest and also here we must consider that in general it will be greater than 5% because not everyone does staking at the same time.

So let's say we call Q the amount of XSPEC that you can get to do staking, then it gives you, in a year a amount that we can call N

N = 0.05 * Q  (N = annual gain in Xspec)
Per month:
N / 12 =(0.05 * Q) / 12 if we call G = N / 12 then it looks like this:

G = (0.05 * Q) / 12 monthly gain in XSPEC

passing 0.05 and 12 to the first member:

G * 240 = Q

Then you can say, I want to earn 100 XSPEC per month, so G = 100 and you should have Q = 100 * 240 = 24000 XSPEC.

But remember that the necessary value will always be somewhat lower than the one calculated with 5%. (you will really earn more than 5%)