Rewards calculated by formula 2222222/(((Difficulty+2600)/9)^2) which is you can find in this post https://bitcointalk.org/index.php?topic=2272607.msg23037625#msg23037625 and masternodes getting reward 20% till block #158000
You can take Difficulty from blocks or from "getdifficulty" command in the wallet. For example block #48705 have Difficulty 177.59786589884 https://altmix.org/coins/13-Desire/explorer/block/48705
Block time is 150 seconds so 24*60*60/150=576 blocks per 24 hours. Number of Masternodes for now is 744 which you can take from "masternode count" command. So reward per masternode per 24 hours is 2222222/(((177.59786589884+2600)/9)^2)*0.2*576/744=3.61 https://www.wolframalpha.com/input/?i=2222222%2F(((177.59786589884%2B2600)%2F9)%5E2)*0.2*576%2F744