How did he do that...

Natasha
My boyfriend and I were having sex and he didn't want to finish inside me and that he wanted me to finish it with my hands. He said that there was no way he could keep going without finishing and then he pulled out quickly and he told me he held it in. Before he pulled out he finished but he didn't completely? He told me he wanted to finish him off and I was confused because he had already somewhat finished inside me... he's like I had to stop it. So I finished him off with my hands and he had the regular amount of cum he normally had which is A LOT. I was also leaking because he finished inside me, but I wanna know... how is that even possible? How does one guy have enough restraint to stop himself from fully cumming??