fire extinguisher rating terms, part one

[joannaingram84]

Fire extinguishers are rated by size of fire (number) and by type of fire (letter). The most common type is "10 ABC."
No. 1: Will extinguish a stack of fifty burning sticks, 20 inches long; or will put a 2.5 sq. ft. area of burning naptha.
No.10: Will extinguish a fire 10 times larger than a No. 1 fire.

source Backstage Handbook: An Illustrated Almanac Of Technical Information by Paul Carter

[Consultsone]

Is this for a safety class or in service?
The ratings need to be more clear in my opinion. Most people don't have the time or ability to hold their stress back to take a moment to read the label.
I have seen times when people make the fire worse or use the wrong one and ruin what could have been salvaged if the right extinguisher was used.