Read your inversion table instructional manual thoroughly before attempting to use the table. It will support your body weight, so it is important that all the steps are done correctly. Make sure you have a friend with you when you use the inversion table for the first time, in case there are problems.
Inversion tables only decompress your spine while you’re using the table. Once you return to a regular position, gravity pushes everything back together again and creates the same pressure on the nerve.
You do not need to do a full 90 degree inversion. Many people do not invert more than 60 degrees, and others use a 30 degree angle because it is more comfortable and you still see benefits.