When the video card mines it performs work, 1 unit of work is called a share. Here we described how PPLNS and PPS+ reward systems work. 

Stale-share is a share that was sent to the pool later than it was required. 

Stale-shares may be caused by delays in the network (ping), you can try to decrease the amount of stale shares by improving network quality in your mining farm (change the network provider, use cables, invest in a better router etc.)

You can’t eliminate the Stale-shares completely, but you can bring down the amount of stale shares significantly.

Stale-shares also bring some income to all miners of the pool, but this type of shares can only produce Uncle-blocks.

Uncle-block is a block with a reduced reward 0.5 to 1.75 Ethereum (instead of regular 2 Ethereum). This block doesn’t include additional rewards and MeV.

Since a Stale share can only bring the reduced reward to the miners of the pool, we pay 80% of the regular share rate for the stale share submitted to the pool. Which means 1 Stale share = 0.8 of the regular share. 0.8 coefficient applies for both PPS+ / PPLNS systems.

In this example our miner sent 18034 shares in total, 245 of them were Stale shares, which equals to 1.36% of all submitted shares.

1.36 х 0.8  1.09% 

98,61 + 1.09 = 99.7%

As the result of stale shares submitted to the pool the total income of this miner was reduced by 0.08%.