The poem is a two-part snapshot of anxiety on an ordinary morning. The speaker has been up, or at least marked, by a bad night, and now spends the morning "sitting with" what it left behind. Calling that leftover "bland merchandise" is a striking choice. It makes the night's worries sound like cheap goods on a shelf: dull, mass-produced, nothing special, yet somehow still the speaker's to carry around all day.
The second line shifts the mood. Studying arithmetic suggests a search for order, something with clear rules and answers when the mind feels unsteady. But the speaker doesn't say they study it to learn; they study it "to see myself." Numbers become a mirror, though a cold and oddly flat one. The poem leaves us with a quiet, tired, slightly detached feeling. Nothing dramatic happens, and that's the point: anxiety here is a low hum, handled through small, careful tasks.