Perigee-syzygy Moon coming up on Monday

This is last month's supermoon. The full Moon on Monday will be even bigger apparently. The term "supermoon" comes from astrology. The Moon has an elliptical orbit around the Earth (oval!) so the Moon is not always the same distance from the Earth. Perigee is the name for the shortest distance between the Moon and the Earth on this oval orbit. Syzygy is the name for when the Sun, the Earth and the Moon are in line. This is true for a full Moon (but also for a new Moon). The thing I'm struggling with is that the perigee distance itself is quoted as a range, sometimes closer than at other times.