By editing the values, you can change the TTLs of one or more record types.

Usually there is no need to change the TTL of your resource records. Just set a reasonable default value in the SOA MINIMUM field, and it will be used for all new records.

One situation where you may want to change the TTL is when you know in advance that there will be a change to DNS data; for example, that the IP address of a machine will change. In this case, it is useful to decrease the TTL of that machine's A record well in advance so that the old data will expire more quickly from caching name servers when the change actually takes place. Remember to restore the original TTL value after the change.