# Intuition behind standard deviation greater than mean for all positive values [duplicate]

I am following through this example

But it doesn't talk about what does it mean when the standard deviation is higher than mean when all values are supposed to be positive e.g. standard deviation of age of 500 people. Clearly age can't be negative but the lower end of 1 standard deviation confidence interval is negative.

Edit: My question is what does lower end of confidence interval being negative mean since negative age is not possible.