Change the automation name to what yours is called and set the 600.0 at the end to however long you want to block execution in seconds.
I have also seen where people put the script/automation into single execution mode and then put a wait at the end for x seconds, this however doesnt work if you reboot/restart HA.
The first part you listed is just taking the current time and minusing the last time the automation was run, which gives you in seconds how long since it last ran. You then compare the result to whatever value you want to exceed before allowing the automation to run again. E.g. if you only want to run once a day, you probably dont actually want 24 hours, or it might not run when you go to bed early, so perhaps say 18 hours, so therefore change 600.00 to 3600 (seconds in an hour) * 18 = 64800.0
The default part just returns 0 if no value is returned by the attribute last_triggered (e.g. it hasnt run before).
Default(0) just means if the value is for whatever reason invalid, it will substitute it for 0. Not overly necessary, but if the automation has never been run it will fix it dropping an error. It is then cast as a float value.
Lastly it takes the whole left of the equation and checks it is greater than 600.0 seconds.