210 on a sport shot
800 series
230 on a house shot
300 game
7-10 split
Why is the 7-10 last? Why is it the easiest? Because there's no "skill" involved in picking it up. Same with the Big-4. Same with a hole-in-one. It's all luck. Grandma can make a 7-10 split, 110-average bowlers can make a 7-10 split. But they can't shoot 300, and they certainly aren't going to shoot 800.
Why do the pros typically have so many Big-4s and 7-10s compared to the rest of us? Well, if nothing else, because they have more opportunity to make it. If a full-time pro bowls only 1000 games in a year, I'd be surprised. Between practice and tournaments, it's probably more like 2000. Go bowl 2000 games a year (about 6 games a day) and see how many 7-10s you leave and have the opportunity to make.
SH