Because it shows how long it takes to kill bacteria and viruses. Some products can kill certain bugs in seconds, whilst other products could take minutes to kill the same bugs. It is vital you adhere to the timeframes listed. CHL disinfectants are typically much quicker at killing bugs than traditional disinfectants.

Further reading:

  1. Have I been cleaning all wrong-? Parker-Pope, Apr ’20   NY Times
  2. Why does contact time matter- NNPHI