Every day in the crowd calendar has a 1–10 score for each park, ranked against that park’s own history from the wait times we record every minute. A 3 at one park and a 3 at another are each a lighter-than-usual day for that park — not the same number of minutes in line.
So the guide never compares parks with each other. For each park it ranks your trip days from lightest to busiest (ties share a rank) and turns that rank into a 0–1 position within the park. The recommended plan is the one with the lowest total of those positions across all your visits, with each park getting exactly the number of days you asked for.
When two plans total the same, it prefers fewer days relying on unpublished park hours, then lighter days for the parks you listed first, then a fixed date-and-park order — so the same choices always give the same plan.
Days with no crowd score are never counted as light: they are left out of the recommendation and only appear in a separately labelled option. Rest days and fixed days are always kept. If your choices can’t all fit, the guide tells you which one to change instead of making up a plan.