You run dig codingshell.com and get the following result:

This is the TTL. When you lookup for an address using a domain/host name, your OS is performing DNS resolution by contacting DNS name servers to get the IP address of the host/domain you are looking for.

When you get a reply, this reply in cached in your OS for a certain period of time. This is period of time is also known as TTL and this is the meaning of 3515 number - it will be cached for 3515 seconds before removed from the cache and during that period of time, you'll get the value from the cache instead of asking DNS name servers for the address again.