Your shared masternode rewards will be equal to your share of a daily masternode reward, proportional to your percent stake in the masternode, minus StakingLabs' 5% fee.

Stakinglabs Shared Masternode Rewards Calculator: https://colx.ciwox.com/calculator-shared-mn

It can be calculated as follows:
(B / N) * R * (P / M) * (1 - F) = A B = blocks per day (1440)
N = current number of masternodes (currently 216)
R = current masternode block reward (570)
M = number of coins required for MN (10,000,000)
P = personal coins in shared masternode
F = Stakinglabs fee (5% or .05)
A = average masternode rewards earned per day

Example: If I have 750,000 coins on Stakinglabs, I will earn 270.5 COLX per day on average: (1440 / 216) * 570 * (750,000 / 10,000,000) * (1 - .05) = 270.5