I think I've figured it out.
:clock-in t is intended for capturing the time you spend on writing the item. So the clock starts as soon as you start writing/capturing, and ends as soon as you C-c C-c to finilize/stop-writing.
if you want the clock to keep running after finalizing, you need to use :clock-in t :clock-keep t.

@sparedwhistle@lemmy.ml the way to to use this is with an org-headline or task. For example you have an org document with "*TODO Write 500 words". When you start the task 'M-x-org-clock-in' whilst your cursor is on the headline and when you finish 'M-x-org-clock-out'. You'll see a timer running in the modeline and It'll take care of the properties for you on completion.