If the pool on current round does not find a block, miners shares are keep (up to 500 blocks), but their value is reduced by 50% everytime we do not find a block. When the pool has positive balance, all the shares are summed up. The burst payments are proportional to the total share miners own at this time.
The payment is only sent the block has 4 confirmations
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 Block0-BaseTarget / Block#N-BaseTarget