Hopefully the attached image clears things up (note I do not have one of these so I am guessing a little bit).

I have made the assumption that the two bit the blue arrow points too are tapped holes, the longer bolts would then be used through these holes.

The bottle cages can then be fixed to the green holes (using one cage) or the red holes (both cages) using the shorter bolts.

Again, this is an educated guess but should work from what you have posted.

Edit: images added

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