Complex sentence: All Mercury grazers have semi-major axes larger than Mercury's (0.3871 AU), and hence are outer grazers, i.e. have perihelia within Mercury's aphelion (0.4667 AU) but not within its perihelion (0.3075 AU).
Split into simpler sentences: All Mercury grazers have semi-major axes larger than Mercury's (0.3871 AU), and hence are outer grazers. I.e. they have perihelia within Mercury's aphelion (0.4667 AU) but not within its perihelion (0.3075 AU).