What does it mean when your systolic blood pressure is high but diastolic pressure is normal range?

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So at my appointment my BP was 136 over 64, which I know isn't super high but my normal range is 100-110/60-70. It wasnt mentioned in the appt but I noticed it in my online chart. What does it mean? Is it anything to be concerned with? My last few BP readings at appts were 104/69, 102/61, 108/68 so all nice and low.