In this guide
A range first, a pattern secondWidth and percentage widthMeasured-move arithmeticWhy ranges can be useful for educationA range first, a pattern second
The core fact is simple: values have remained between chosen boundaries for some interval. Calling the structure a rectangle adds a visual label but does not change the underlying measurements.
Width and percentage width
Subtract the lower boundary from the upper boundary to obtain absolute range width. Divide by the lower boundary to express the same width as a percentage. These calculations are independent of any future move.
Measured-move arithmetic
Some chart methods project the range height from a breakout boundary. If the range is 90 to 100, the height is 10. An upward projection from 100 is 110 and a downward projection from 90 is 80. Those are formula outputs only.
Why ranges can be useful for education
Rectangles make it easy to separate subjective boundary selection from objective arithmetic. Once two boundaries are chosen, distance, width and projections can all be checked by hand.