The #NUM you see in boxes D2 and I2 are because no computation has taken place yet!
Input you date of birth into boxes A2, B2, and C2 in the same format as I've inputted yesterday's date into boxes E2, F2, and G2.
Computations will then occur and your age will appear in box I2.
The number you see currently in H2 is the serial date in number format for yesterday's date.