Rekha drew a circle of radius $2\;\text{cm}$ on a graph paper of grid $1\;\text{cm}\times1\;\text{cm}$. She then calculated the area of the circle by adding up only the number of full unit-squares that fell within the perimeter of the circle. If the value that Rekha obtained was $d\:\text{sq cm}$. less than the correct value, then find the maximum possible value of $d?$
- $6.28$
- $7.28$
- $7.56$
- $8.56$