The total number of honor guards is 500, and the solution is as follows:

Solution: let the total number of people be s, and the number of people in each row and column for the first time be x. According to the meaning of the question, the following two formulas can be listed:

S=X*X+ 100

S=(X+3)*(X+3)-29

The above two formulas want to simplify:

X*X+ 100=(X+3)*(X+3)-29

Solution: x=20

Therefore, s=X*X+ 100=500.