This is a great question and you are right to be confused! Florida statutes define "weapons" and provide an exception for the "common pocketknife."
The statute (790.001(13)) does not, however, define what exactly a "common pocketknife" is or is not. At one point, a juvenile, such as yourself, being prosecuted under the weapons statute for carrying a small knife appealed their conviction. The case is L.B. v. State of Florida, 700 So2d 370 (1997).
In that case, LB challenged the weapons exception statute definitions found in 790.001(13) as being unconstitutionally vague and ambiguous, meaning that a normal person could not tell what was illegal and what wasn't based only upon the words "common pocketknife," just as you have found. When a person cannot tell what is allowed and what is not, it is unconstitutionally vague for denying "notice of proscribed behavior" and therefore denying due process to the citizen. Both notice and due process are rights guaranteed in the constitution.
In the case of LB, the appellate court in Florida found the term "common pocketknife" wasn't too vague or ambiguous and that it just needed a common sense interpretation. In the case of L.B., the court found that any knife that folded and had a blade less than 4 inches and a total length when open of less than 81/2 inches would normally fit within that definition and thus be exempt from being classified an illegal weapon under Florida Statutes. These dimensions they had gotten from the Attorney General of Florida's 1951 definition of a pocketknife.
LB's knife had a blade that was 3 3/4 inches long and an overall length that was within the stated 8 1/2 inch limit and so his conviction was overturned.
This is a great example of how courts' interpretation of statutes govern their actual application. Also, you are wise to consider the other statutes that prohibit the use, showing or otherwise threatening application of even a "common pocketknife" as being against the law. See Statutes 790.115 and 790.117, for example.
I think you can answer your own original question from this answer; you seem like a smart young man.
The above is provided for educational purposes only and is not legal advice nor makes you a client of the Mosca Law Firm, PA. Please consult with a lawyer in order to obtain confidential legal advice that is tailored to your specific situation and facts.