Vintage West Bend Slow Cooker number settings verses hi low settings
You should consult the owner's manual for your slow cooker.  According to one manual on West Bend's website:


  There are five numbered heat settings on the heating base, 1 to 5.
  Heat setting # 1 should only be used to warm dinner rolls, muffins,
  etc. Heat setting # 2 should only be used to keep warm cooked foods
  for serving, whereas Heat Settings #3, #4 and #5 are to be used for
  actual cooking of foods. Set the dial directly at the numbered heat
  setting or midway between the numbered heat settings for complete
  temperature control. DO NOT USE A HEAT SETTING BELOW # 3 FOR ACTUAL
  COOKING OF RAW FOODS AS SLOW COOKER DOES NOT GET HOT ENOUGH TO COOK
  FOODS AT SETTING #1 OR #2. Set heat setting and cook food for
  recommended time as given in recipe. As a general guideline, most meat
  and vegetable combinations need 7 to 10 hours of cooking at Setting #3
  (low), 4 to 6 hours of cooking at Setting #4 (medium) or 2 to 3 hours
  of cooking at Setting #5 (high).


Your particular model might have different instructions.