The term markup refers to the percentage that a stakee adds to his staking rate.
For example, the stakee offers a 50% share of a tournament package at a rate of 1.2:1. He therefore gets 20% more, but only pays out 1:1. The markup can either be paid upfront or deducted in the case of a win.
Player A offers the stakers a package worth 1,000$ and pays 50% himself. He decides on a rate of 1.2:1 and wants $600for the 50%. Effectively, player A only pays 40% of his package, but if he wins, he receives 50% of the profit.
Player A offers the stakers a package worth $1,000 and pays 50% himself. He decides on a rate of 1.2:1, and the stakee will only deduct the markup in the event of a win. Every staker then pays the rate of 1:1 for the staking as such, but if the player wins, each staker will only receive the following amount:
1 (Winnings) / 1.2 = 0.8333 = Net profit of each staker.