ELI5 Shares and Estimated Payout

Please explain to me like I am 5 how my shares are nearing 300 yet this estimated payout was capped 12 hours ago. This is the reason why I stopped mining on pools other than 2miners. They had lower payouts despite what looked like a higher share count. It makes no sense to me and because I’m trying to eek my way through on 1 GPU I don’t have the luxury or luck to go solo.