A normalized factor scales the toy coupling without claiming hardware constants. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
A coupling factor scales the toy budget
The raw product is 6 joules and the normalized factor is 1/2.
21⋅6J=3J
The factor is not a hardware constant
The accepted toy coupling is 3 joules, but the lesson does not name a real junction constant.