The correct reading is めんみつ, with both 綿 (メン) and 密 (ミツ) using their On'yomi. 綿, literally cotton, implies fineness. Incorrect readings misread 密 or 綿. It describes something detailed, meticulous, or done with great care.

「綿」は「メン」、「密」は「ミツ」と両方とも音読みです。「綿」は細かさや丁寧さを表します。「めんびつ」や「べんみつ」は誤読。非常に細かく、注意深い様子を表します。