if pool on current round does not find a block, miners shares are keep (up to 360 blocks),
but their value is reduced by 50% everytime we dont found a block.
when pool has positive balance, all share are summed up to block# where payment will be made,
and burst payment are made proportional to total share miners own up to this time
deadline value from miner is converted into share value using this equation
share = 1000 / ( NetDiff * Deadline + 1 ) 0.75
where NetDiff (Network Difficulty) is calculated by 18325193796 / BaseTarget
note : to prevent user spamming low share, there is a request limit.