Malbim: There were 4,000 gatekeepers (23:5). Each week, only 168 came to the Mikdash; the rest stayed in their cities. In 24 weeks, there were 4,032; the verse was not precise (it omitted the extra 32 ¹ ). The calculation here matches Nechemyah 11:19, which says that there were 172 gatekeepers; that includes the four appointees Shalum, Akuv, Talmon and Achiman (above, 17). Nechemyah did not count the appointees over the storehouses, Kelim... (refer to 9:22:1:2 and the note there), so it counted only 168 [and four]. Here it includes the others, so there are 212.

'Rashi': Each Mishmar stayed for seven days.