I’m pretty sure you are right except that it doesn’t add the full extra 6 minutes and 40 seconds it just continues until then from where the specified death was written
Isaac Perry
2023-06-05 01:14:58 +0000 UTC
Now I could be wrong, but here’s how I understand it
Write Name (no specified death) - Heart Attack in 40 seconds
Write Name (Specific Death) - Has to be Written in 40 seconds, once the Death note senses there’s a specified death, a 6 minute 40 second timer is given to give specified details of the death such as time or details leading to the death, which was how Light was able to kill prisoners on the hour, without having to pull out the Death Note everytime he needed to kill someone. It will basically delay the death unless he could specify for it to happen more immediately.
If that ain’t right, I’m as confused as you 😂