@David ******
it is what it is, and Ellie wanted to point it out to you in case you'd already taken the 60 day visit thai family extension earlier on your visa process for the visa you're on as that would mean you can't use it again.
If you haven't taken it before on this visa/extension you're on now you're fine getting it
The 30 day extension for free stamp and tourist visa entries is also one time per entry.