Count the arrows
The most common counting mistake is to include the starting word as a move. A move is a transformation between two words. If a route contains six words, it contains five transformations. The quick rule is: moves equal the number of words minus one.
For the historical example WAYS — BAYS — BOYS — BOOS — BOOP — POOP, count the arrows. There are five. POOP is reached on move five, even though it is the sixth word displayed.
Number your starting position zero
Write the starting word beside 0, the next word beside 1, and continue until the target. This keeps a handwritten attempt consistent with a solver's move count. It also makes comparing two routes easier: the final number is the answer you need.
If you are already at POOP, no transformation is needed, so the distance to POOP is zero. A different valid word one letter away takes one move.
A changed letter is not always progress
Compare WAYS with POOP. All four positions differ, so reaching POOP must require at least four letter changes. That is only a lower bound. The need to pass through accepted words may force you to change a position more than once.
This explains why a four-letter puzzle can require more than four moves. You are not simply replacing the four incorrect letters; you are finding a connected sequence of valid words between them.
Check transitions before comparing scores
Two words count as one legal transition only when exactly one character position differs. Keep both words aligned and compare positions one through four. A jump that changes two positions cannot be counted as a single move, even when both endpoints are familiar words.
Also check every intermediate word against the accepted list. A route with a smaller number of arrows is not a better solution if one of those arrows or words is invalid.
Keep the rule and the route together
When sharing a solution, include the starting word, full sequence, and move count. Readers can then verify the arithmetic and the letter changes without guessing what you counted. If you used a separate solver, mention its word list or any compatibility notice.
Different word lists can produce different shortest distances. An apparent scoring disagreement may be a vocabulary disagreement, rather than an arithmetic error. Check that distinction before deciding either result is wrong.