In just three lines, the poem sets up a small, odd picture: rain collecting in beads on leaves, except these leaves are "numbered," and they belong to a "study group." The last line makes us rethink the first two. The leaves seem to be pages, the sort handed out in a class or meeting, so the rain is falling on paper as well as on a plant, or perhaps the two images blur together.
The speaker doesn't say how they feel, but the tone suggests quiet, patient attention. Someone is noticing a tiny natural detail in the middle of an organized, bookish setting. The poem seems to find a gentle humor or wonder in how nature slips into a place of rules and numbering. The mood is calm and a little playful, like glancing out a window during a meeting and finding the rain more interesting than the page in front of you.