Re: Underneath flammability symbols there is a number what does it mean?

The following table is from the US Department of Transportation  
regulations and gives the numerical code for each hazardous material:

Label Substitution Table
Label code                   Label name
-----------------------------------------------------------
1                            Explosive.
1.11                         Explosive 1.11.
1.21                         Explosive 1.2.1
1.31                         Explosive 1.3.1
1.41                         Explosive 1.4.1
1.51                         Explosive 1.5.1
1.61                         Explosive 1.6.1
2.1                          Flammable Gas.
2.2                          Non-Flammable Gas.
2.3                          Poison Gas.
3                            Flammable Liquid.
4.1                          Flammable Solid.
4.2                          Spontaneously Combustible.
4.3                          Dangerous When Wet.
5.1                          Oxidizer.
5.2                          Organic Peroxide.
6.1 (inhalation hazard,      Poison Inhalation Hazard
   Zone A or B)
6.1 (other than inhalation   Poison Inhalation Hazard
6.2                          Infectious Substance.
7                            Radioactive.
8                            Corrosive.
9                            Class 9.hazard, Zone A or B

So a "flammable" symbol with a 3 means "flammable liquid."