AutoFilter is not filtering properly

I have one column with values 203, 205 and 206. A second column has A, B, C, D, E.

I filter the first column for 206 and the second column filtered for B. The results in that second column shows B but also shows a row with value A. How is this happening?

Then in another try, I filtered for 206 and got 206 but I also got 203 and 205 in that first column? It seems like the problem is getting worse. How does this happen?