When you check your blood glucose you are measuring your level at the time of monitoring. However, your HbA1c result looks at your overall blood glucose control for the previous three months.
Confusingly, HbA1c is measured in a different format called mmol/mol. NICE recommends a HbA1c target of 6.5% (48mmol/mol) to reduce the chances of long-term complications, but it is important that every person with type 1 should set and regularly revisit HbA1c targets in conjunction with their healthcare professionals.