I have Obstructive sleep apnea syndrome, how serious is this?

I am 64. Three years ago, I had a CT scan (or MRI) on my lungs to check for lung cancer (former smoker). It showed I had emphysema. I then went to Mayo Clinic in MI for assessment and was told it was mild and I may never be bothered by it.
Two weeks ago I did a sleep study at home. I did the unattended home portable study.
The Nurse called and said I did not have sleep apnea, but
The report states, “Primary Diagnosis as Obstructive sleep apnea syndrome”.
Report Results are:
02 sat less than 90% 481 minutes, less than 88% 202 minutes. Average 02 sat 88%. Average respiratory rate 12, pulse rate was about 65 plus or minus.
Respiratory events:
No obstructive apneas, 70 hypopneas.
AHI – 7.3 supine for 178 minutes AHI 7.1
Assessment:
Borderline obstructive sleep apnea G47.33
Hypoxemia G47.34
Recommendations 02 at 2L/min
Nocturnal oximetry study at 2 L/min

My question is, How serious is this, am I going to be dragging around an oxygen bottle in a couple of years?
How could I have “obstructive sleep apnea syndrome or Borderline obstructive sleep apnea if the results showed “no obstructive apneas?”
Being my AHI was 7.3 does that mean my case is “mild?” Is my oxygen saturation of 88% really bad?
I am 20-25 lbs overweight.