Your HbA1C test measured the amount A1C type haemoglobin in your blood, also known as glycosylated haemoglobin.
HbA1C is used to test for diabetes. Diabetes is a condition where there is too much sugar (glucose) in the blood and traditionally doctors have tested the blood sugar level or even just tested whether the level is so high it overflows into the urine. However, blood sugar levels go up and down depending upon intake, particularly in diabetes so the traditional tests are not always reliable.
Since glucose binds reversibly to haemoglobin in the red cells and since the lifespan of a red cell is three months, the HbA1C gives a measure of your average blood sugar level over the past three months. This is precisely what is needed to check reliably for diabetes and since your level is below the recommended limit, you can be confident your blood sugar has been at safe levels.