What does low renin level mean?

I was admitted to ER about 2 weeks ago because of high blood pressure. I was there for my yearly checkup when the doctor sent me to ER right away and they prescribed me high blood pressure medication. My blood pressure had always been around 130/90; hence my doctor never prescribed me anything; but it went to 180 and I felt okay (no headache or any hypertension symptoms).

They did EKG, blood, and urine test and the results were all good, except very low potassium level. So, my doctor prescribed me HBP meds and encouraged me to consume 2 bananas/ day and take a rest (I slept about 5 hours each day).

Last week, I went for my adrenal gland test and I just saw the result:

- normal blood pressure (I'm still taking prescription)

- good sodium level

- good potassium level (I've been eating bananas, spinach, yogurt every day), but

- low renin levels (I'm 0.10 below good result).

I'm waiting to hear back from my doctor for the next step, but I'm curious to know what's that supposed to mean and what's causing it.

Thanks!