There should be 2 release disc on your Reg. one for tank release which should be 4.5k and the reg max at 1.8 k. If your reg is made with bellville washers then you can shim or reconfigure the washers to any pressure below 1800 psi. If the tank is empty , you can then remove the set screws and unscrew the top to examine the spring. Most paintball shops will have shims. If it has a coil spring there is not much than can be done. I have shims in .01mm .02mm and .03mm and bellville washers in 2 different thicknesses.
I have purchased quit a few regs from china for 4500 psi tanks with preset at 1800 psi, I have then fine adjusted them for my needs. I have 1 left that is on a 4500 psi tank set at 1500 psi that was for my Gauntlet on range days. I have purchased them from here
https://www.aliexpress.com/item/1005005184634671.html?spm=a2g0o.productlist.main.21.292e5c5axcaFGA&algo_pvid=bc17921e-a6e7-47c3-b9a9-855f96a09fed&algo_exp_id=bc17921e-a6e7-47c3-b9a9-855f96a09fed-10&pdp_npi=3%40dis%21CAD%2135.7%2117.49%21%21%21%21%21%4021227e5116829666044602448d07c6%2112000032018754369%21sea%21CA%214381166741&curPageLogUid=0Bvb5cL01oRiBob has done a write up on his shimming with Ninja Regulators you will find it, if you do a search. My work on regs have been with multiple brands and they are all very similar.
Depending on the type of paintball shop in your city-town they may have they ability to shim or reconfigure. If you over shim the reg the valve will not close and the air will go to max pressure and burst the disc. I have a micro bottle and a gauge block so I can use only a small amount of air and test the output pressure. Sometimes it may take 3 tries to get the exact desired pressure.
Hope this helps
Robert