There was a democratic runoff in the extreme northeastern part of Hinds County on June 24. Mississippi’s 3rd Congressional District includes the northeast corner of Hinds County. There was a runoff between Doug Magee and Dennis Quinn. I would guess the photo of the ballot page everyone is referencing is a photo of a poll book from one of those precincts.
This northeastern corner of Hinds County includes parts of the city of Jackson, thus the Jackson addresses on the poll sheet.
That was my first thought. However, it most certainly isn’t the case.
That page is from Precinct 61 in Hinds County (part of Jackson, MS) and the voters are from the MS 2nd Congressional District (USH02) not USH03 where the Democrat runoff was held.
Further, the poll books were switched between parties for the runoff. So the Republicans used the Democrat primary poll books for the runoff and the Democrats used the Republican primary poll books. They did so to prevent cross-over voters because the poll workers could see immediately whether or the voter voted in the Democrat primary.