Original sentence: It usually follows a 33-year cycle with occasional interruptions by single 29-year or 37-year cycles.Over the long term this will equate to the mean tropical year (365.24219 days), which is why a great grand cycle of 2820 years has been  proposed, made up of 22 grand cycles (made up in turn of four small cycles).Since the calendar uses astronomical calculation for determining the vernal equinox, it has no intrinsic error, but this makes it an observation based calendar.The difference between observed and mean vernal equinoxes is never more than a day or so, which is why the small cycle of eight leap years in 33 predominates in either case.The reason for this behaviour is (as explained above) that it tracks the observed vernal equinox.This determination of starting moment is more accurate than the Gregorian calendar as far as predicting the date of the vernal equinox is concerned because it uses astronomical calculation rather than mathematical rules, but requires consulting an astronomical almanac
Edited sentence: By contrast, some less accurate predictive algorithms are suggestion based on confusion between average tropical year (365.2422 days, approximated with near 128-year cycles or 2820-year great cycles) and the mean interval between spring equinoxes (365.2424 days, approximated with a near 33-year cycle).It usually follows a 33-year cycle with occasional interruptions by single 29-year or 37-year subcycles.Since the calendar uses astronomical calculation for determining vernal equinox, it has no intrinsic error, but this makes it an observation based calendar.This determination of starting moment is more accurate than the Gregorian calendar because it is synchronized with the vernal equinox year, but requires consulting an astronomical almanac