Hi, Welcome to HCM,
Its good that you are doing your yearly physical examination. As all the tests are normal, you should not worry much about.
in urine, there can be many normal causes for this like a very minor injury
in genital tract and in females, it can be due to menstrual blood.
It can be due to some vigorous exercise or a very tiny stone also.
Your doctor have advised the right thing to repeat the test one week later.
Regarding severity, it can be measured with the number of rbc
in urine and amount of hemoglobin on an automatic counter.
Would advise you to just relax and do a repeat testing and consult your doctor.