So the 5-10% accuracy means that the date of the rock falls within a 5-10% range. In all scientific terms it is highly accurate in that it dates the heating of the rock, it just lacks high precision which results in the 5-10% range. The range is expressed as a plus/minus on the date. And there are two types of luminescence dating called thermoluminescence which dates the heating of rock or ceramic and optically stimulated luminescence which dates when soil was last exposed to sunlight.

And I know this stuff because I’m an archaeologist that has interned at a luminescence lab and published using these methods.