In terms of accounting, for users staking into a vault after the start of the vault’s entry/exit window, a joining fee is calculated and applied to the staked balance upon entry to adjust their revenue share weight fairly.
The fee is equivalent to the rewards that would have been earned up until the point of entry, had they been staked from the beginning.
In simple terms, the fee is calculated as a percentage of the estimated rewards you would receive at the end of the vault cycle, applied per day. For a 1 month vault, the fee is ~0.038% per day.
To illustrate the concept, consider the following:
Templar A joins a vault on day one with 1000 $TEMPLE, the start of the entry exit window. No fee is taken because this user will be staking for the entire vault cycle.
Templar B enters a vault on day seven with 1000 $TEMPLE. Since this Templar is entering six days late (the last day they can enter the vault), they will incur the max joining fee calculated as such:
0.038 x 6 = 0.23%
We then take this percentage and multiply it by the amount of temple deposited to determine the fee in $TEMPLE
0.23% x 1000 = 2.3
Hence, a joining fee of 2.3 $TEMPLE will be applied for Templar B and the balance they enter the vault with will be 997.7
$TEMPLE. 1000 - 2.3 = 997.7
Templar B has a slightly lower final revenue share weight for the vault cycle due to not being staked as long during the vault cycle. This design ensures a fair system for early stakers in any given vault that have earned a little more than those who join the vault later. The joining fee amount for any given entry is always visible on the “Stake” section of the vault user interface, so users can always see the information before staking.