四分律行事鈔資持記 2.635

2.635

樹界中，初文。與人等者，示高量也。蔭跏趺者，即廣量也。此相極小，已下非用，故注示之。

Regarding the boundary of a tree: in the opening passage, "equal to a person [in height]" indicates its measurement of height. "Casting shade [broad enough for sitting] cross-legged" indicates its measurement of breadth. These marks are extremely minimal, and anything below them is not to be used; hence this is shown in the note.