Another Millis Timer off question...

@ Coding Badly
@ DKWatson

Easy now, fellas. No need to make a stink over this.

I did try isolating the millis with additional parenthesis, to no avail. I've tried various iterations but nothing seems to work for me. I've read several online examples. I'm missing something in the order or sequence, I think. And I'm a noob, so.... hence why I'm here.