Historically this caused a lot of confusion, so you aren't the only one. You may find E. Jaynes' classic paper on the Gibbs mixing paradox helpful, especially

Historically this caused a lot of confusion, so you aren't the only one. You may find E. Jaynes' classic paper on the Gibbs mixing paradox helpful, especially from page 7 onwards: https://www.mdpi.org/lin/entropy/cgibbs.pdf https://www.mdpi.org/lin/entropy/cgibbs.pdf