To be honest, I had to Google to see what a Cuban chain looks like and from what I see, it’s simply a heavy flat cable chain. So if you need to adjust the length, it should be just a matter of removing a link or two.
Check to see if the links are soldered. Quality chains usually have soldered links and if they are, it complicates the process. However, if upon examination you find that the links are open, you simply need to open the link by twisting the ends to the sides with jewelry pliers and remove however many you need to shorten the chain sufficiently. I would open the link next to the jump ring on the clasp, determine how many links to remove, then reattach the chain to the jump ring.