CalculateIntervalSizeProvider can provide intervalsCount + 1 points(intervals)

synthetic example.
intervalsCount = 7; 
minTime = 1;
maxTime = 123;
was => interval size = 17
17 * 7 = 119 . that means that there will be one more interval to cover last point(s).
is => interval size = 18
18*7 =126. - all point covered.