You've got the Clock column for time, ppm H2 (hydrogen), and ppm CH4 (methane). So your numbers for methane are 0 at all times, and for hydrogen, you've got a range of 1 to 6.

It's not that your numbers are negative, but that you haven't reached a high enough hydrogen and/or methane response to indicate SIBO (some people produce hydrogen, some produce methane, some produce both). For a lactulose SIBO breath test, which I believe is the most common, you have to hit 20 ppm of hydrogen and/or methane to indicate SIBO.

 

Positive diagnosis for a lactulose SIBO breath test - typically positive if the patient produces approximately 20 ppm of hydrogen and/or methane within the first two hours (indicates bacteria in the small intestine), followed by a much larger peak (colonic response). This is also known as a biphasic pattern. Lactulose is not absorbed by the digestive system and can help determine distal end bacterial overgrowth, which means the bacteria are lower in the small intestine. The excess hydrogen or methane is assumed to be typically caused by an overgrowth of otherwise normal intestinal bacteria.