If you are using a timer function on a phone, rather than stopwatch function, you are using the digital equivalent of a countdown timer.
I use a countdown bezel for both cooking and takeout, on an infrequent basis. If I need to let something cook for longer, I'm less interested in total cook time, and it's easier for me to figure by end time, plus additional... or since the countdown bezels I own are bidirectional, simply add more time.
For takeout, I set for when I need to leave the house for pickup, no problem - I don't have to remember to leave at... how many minutes elapsed, again?
OTOH, the 12hr scales on the countdown bezels I prefer, give me an option for rough count-up timing as well.
I've also seen 12hr/dive timer bezels, too, but one thing that seems rare it nonexistent is countdown/count-up.
This one's pretty interesting, though:
With the 30 replaced by a triangle marker, in effect it can be used as either countdown or count-up. Slick...