In my experience, a lot of formulas, conditionals and maths work in the web preview but not in the watch or phone preview. Web preview is, sort of speaking, more permissive.
But, I just checked out and it works perfect in my phone preview (android) and in my watch (fossil q explorist)
@rarest Ive noticed sometimes when the watch is not syncing or running a face properly that it needs rebooted. Watchs are limited on memory and often gets bogged down. I have a samsung s3 frontier and it will become very stubborn on some apps or faces. But once i turn it off and back on it works properly…Just a thought