its like a half life thing, the energy from the UV radiation makes the molecules of the virus shimmy and shake until it breaks, and this is time dependent so for a given |dosage| of UV you need wattage over time at distance from the source. it might be better to hang the garment in a closet or enclosure and expose it for a period of time.

in particular, the cuffs, and the upper chest lapel area, and the hip/pocket area these are typical hotspots.