asymptomatic

what confuses me sometimes is when the signs and symptoms of a disease is kinda contradictory. like for hypertension it says that it is asympotmatic, but is also says, nocturia, headache, blurred vision. I know that sometimes some people have no symptoms, so would that just mean that there hypertension is just not as severe? or some people are just lucky (or unlucky) and don't display symptoms with some conditions.?