How to change file upload directory for image uploads?

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Presently the site I am creating in C5 uploads image files I use in connection with a block called Zoom Image Dual to some mathematicians delight looking directory within the /files directory.

It's all Greek to me when looking at the directory names being used.

7813
6013
9513

Etc. Those directory names are meaningless. I'd like them to all go into ONE single directory off the root called...well.../images. Much nicer and easier to work with.

But...I have Google all over and have searched and searched here and just can't find any information on how to change the upload directory used by default in C5.

Does anyone here know how to do that?

I don't need hand holding just a tip or two about where the present directory naming scheme is at so that I might go in and change it manually or otherwise more to my liking.

I'd really appreciate any tip from anyone.

Thanks.

Carlos