I’m not familiar with the Contour TS meter, but are you sure it is a plasma meter and not a ‘plasma calibrated’ meter? Labs use just the plasma portion of blood to measure blood sugar, but home meters work with a sample of whole blood. A whole blood result is generally about 10 or 12% lower than an equivalent plasma result. Neither result is wrong, they’re just measuring blood sugar using different scales. Think of it as measuring temperature using different scales (Celcius, Fahrenheit, Kelvin, Rankine, Reaumur. Deslile, Newton, etc.). All of the measurements are correct, but you have to convert them to compare them to one another.
Many (most?) home blood sugar meters are plasma calibrated whole blood meters. They measure whole blood but convert the reading to the plasma scale so that the results can be compared directly to the plasma blood results from lab tests.
You can us either type of measurement as long as you are aware of which it is. Some sources give different targets depending on the type of meter you use, but many only give a plasma target (or at least I think it is a plasma target).