I agree with OP that it's unnecessarily confusing. A "method" is a procedure. The floating point number is the result of that procedure, not the procedure itself.
"Decimal" implies a ten based system, even though it's perfectly fine to say "binary decimal".
Using your own replacement words, it would be clearer to write "A floating point number is a representation of a number with a fractional part".
Maybe it should've said "is a method of storing" instead of "for". It would make it clear it's not talking about a procedure, but a way or manner of doing something.
"Decimal" implies a ten based system, even though it's perfectly fine to say "binary decimal".
Using your own replacement words, it would be clearer to write "A floating point number is a representation of a number with a fractional part".