This is completely normal. When he ejaculates the sperm goes exactly where it needs to, and what's left is just expelled from the body. Some people say (including some doctors, actually) that laying with your hips elevated for 20-30 minutes after intercourse helps - but this scientifically makes no difference at all. It gets to where it needs to without needing to do anything else - our bodies are build for this.
I'd be more concerned if it didn't leak out lol. There's plenty sperm getting to where they need to go. All the rest of the fluid needs to come out.
It's not a condition its perfectly normal. A lot of the sperm still gets to where it is needed. Good advice is afterwards lie on your back with a pillow under your bum and legs up.