Thank you for your feedback!

The Kurtosis of a normal distribution is 3.0. and it's because of the way the formula for Kurtosis works out.

Kurtosis minus 3.0 is called excess Kurtosis. So if the distribution's Kurtosis comes out to 4.0, it is said to have an excess Kurtosis of 1.0. If the Kurtosis comes out to be a perfect 3.0, it's excess Kurtosis is zero, meaning it's perfectly normally distributed. Hope it's clear now.