19 to 20 is one, 20 to 21 is two. 19, 20, and 21 are three numbers, but the space from 19 to 21 is two movements, er go a two year gap
5
Anonymous#41d
The same way a 5-point line has four segments connecting its points, the number of segments or movements is always one less than the number of states or values. Like how a trip connecting two places is one trip, or a road connecting two buildings is one stretch of road