A diamond is a sighting mark on the frame. Its physical location and the number assigned by an aiming system are different things. Identify both before calculating.
Start with physical spacing
UMB equipment rules place marks at intervals of one eighth of the playing length. On a 2.84 × 1.42 m surface, that interval is 35.5 cm: eight intervals along the length and four across the width. Count intervals rather than inventing a continuous perimeter number sequence. Optional corner marks do not define a system’s values.
A coordinate example
Choose the lower-left playing-surface corner as (0, 0), x along the length and y across the width. Halfway along and one interval up is (142 cm, 35.5 cm); the far corner is (284 cm, 142 cm). These are distances, not Corner-5 values. A ball centre also stays at least its radius inside the cushion boundary.
Through a mark or at the cushion?
A frame mark is behind the cushion nose. A line aimed through it may meet the cushion at a different lateral point from its perpendicular projection. Read the chart’s convention: departure can be obtained by extending the actual aiming line backwards, while arrival may be read at the nose. Do not silently substitute one reference for another.
Translate one complete chart
For Corner-5, label departure D, first-cushion aim F and third-cushion arrival T on the matching diagram. T = D − F belongs to those scales, not a single perimeter count. Changing 5−3=2 to 50−30=20 changes units only if all scales change together. Plus uses a different reference pattern.
A practical reading exercise
Save one app layout and write the coordinates, intended first event and cushion order. Identify a physical marker and a chart value separately. Replay and note actual contact locations. Repeat with only aim changed. This separates a chart-reading error from a different rebound; it does not promise a learning-speed multiplier.