Read https://en.m.wikipedia.org/wiki/M202_FLASH
Essentially, it should be meant to force enemies to abandon a position for 5 to 10 seconds to enable an attack.
The M202 FLASH ("Flame Assault Shoulder") is an American rocket launcher manufactured by Northrop Corporation, designed to replace the World War II–vintage flamethrowers (such as the M1 and the M2) that remained the military's standard incendiary devices well into the 1980s. The XM202 prototype launcher was tested in the Vietnam War, as part of ...