Can anyone suggest me why for is the correct answer here?
Propositions vary between languages, it's not a one-to-one mapping.
It depends on you -> Depende de ti
The preposition "on" is translated as "of" in Spanish.
Moreover, "de" can be "of", "from", "by", "with", "at", and many more.
There isn't an objectively correct answer about prepositions, such as in mathematics 1+2=3, which is correct for everyone.
You simply have to memorize when to use "for".
That said, you could think of the usage as an abbreviation "The figures for analyzing train and bicycle use" or "The figures for tallying train and bicycle use" or "The figures for the purposes of counting train and bicycle use"