Something of a rule of thumb tends to be that "precursor" javelins amount to about 2-3 a nose, since obviously the soldiers are expected to toss them at the enemy before closing into hand-to-hand combat rather than having to deal with the minor inconvenience of a clutch of still-unused javelins in the shield hand during close combat.

As for why the Thureophoroi and the Thorakitai are armed with the exact same javelins despite explicit description to the contrary, um. Bit of an extended lapse in the statting process there, some mea culpa too.