The synodic month (which is the familiar one) is 29.53, the sidereal month is 27.something. :^)
The period of the moon’s “elliptical” orbit is the anomalistic month, which is different, also. The anomalistic month determines the moon’s variation in angular diameter over the course of a month. The moon’s orbit changes shape, or eccentricity and the perigee moves slightly. I am not sure what 26.5 represents.
https://en.wikipedia.org/wiki/Lunar_month#Types
Month type Length in days (in year 2000)
draconitic 27.212220815
tropical 27.321582252
sidereal 27.321661554
anomalistic 27.554549886
synodic 29.530588861