四分律行事鈔資持記 2.639

2.639

上下中。引《了論》正取樹相，樓是相因。上落下者，言有此義，不必須落。

In "above and below": citing the Vinayadvāviṃśatividyā-śāstra, it primarily takes the marks of a tree, while a multi-storied building is an attendant cause. "Falling from above" means that this circumstance applies, but it does not necessarily have to fall.