Help with Type converson (casting)

I am trying to read though this book so i can learn some stuff on my own before i start going to school for it so i know next to nothing. So Here's my question there are 2 collums

Expression Evaluates to
static_cast<int>(7.9) 7
static_cast<int>(3.3) 3

there are more examples, but i figure 2 are enough basically i don't understand wht the numbers evaluate the way they do and the book dosen't explain anything.

7.9 and 3.3 are floating-point values. You then cast them into integer values. Since integer values cannot represent precision beyond the whole number, everything past the decimal point is thrown away.