It´s only work solong the price not go to much down or not come more Masternodes!
It´s calculated with the price and number of Masternodes actual

expl.:
1 ADR cost 0.00002 BTC then you buy a Masternode at 0.02 BTC ~$160

1440 Blocks a day with now 326 Masternodes give you ~ 4,41 Blockrewards a day it´s ~141,35 ADR
in 30 day´s = ~4240,49 ADR so you get ~0.085 BTC
With 500 Masternodes you get only ~2,88 Blockrewards and ~92,16 ADR a day.

This can change to alot factors like your Masternode go offline and you must restart, then you don´t get a reward for ~13 hours.
you never can say i get a reward in 4 or 5 hours, when the math say you get 4 rewards in 24 hours one day can be 3 the next day 5,
when someone pump or dump and the price change extreme the numbers that you see on sites like masternode.online, go up and down, too.
Look the coin and check the values and make your choice, but never trust only the numbers you see on Masternode listing site.