If you look again at the link that you supplied to the Sumter County Appraiser, and actually look at the full property description, you will see that there are three land uses for the property. The first is a piece that is 175 feet by 200 feet deep (0.8 acre), the second is 500 feet by 350 feet (4.0 acre), and the third is the parcel you keep talking about, which is the 0.51 acre piece. These add up to 5.31 acres.
Land Breakdown # Land Use Land Units Frontage Depth 1 US 301/Turnpike (3546C) 175.00 Front Feet 175.00 200.00 2 US 301/Turnpike (3542C) 500.00 Front Feet 500.00 350.00 3 acreage (0131C) 0.51 Acre