Tribex & M

Recently my total T level was about 320. I then started using Tribex-500 and M for about a week and a half. When I had it tested 4 days ago it was 550 total but my doc says that my free T is 9.1 which is low. He didn’t want to elaborate when I asked what this figure meant and how is it derived. Does anyone have an idea what this means and how I can raise my free T?