Answering "How many months of work experience do you have?" on grad school applications I am applying to a MS in a STEM degree (Business Analytics or Data Science) at some pretty competitive US universities (domestic applicant).

I have done a lot of different types of work during and after my bachelors program (coursework completed in 3/17), in a large variety of projects and teams on many different time tables and employment statuses. I'll have a separate question I'll be asking in relation to my freelance work after the period in the image below, but I wanted to see what from my usually listed items on my resume I should consider factoring these into the question "How many months of work experience do you have?"

There are mainly 3 questions here,


How should I tabulate months of experience based on the man-hours I've through put on these projects?
Which of these projects would be considered something I should not count towards a question like that on my graduate applications? 
Is there an implication that I should be focusing on post-graduate work experience for a question like this or any other conventions I should be cognizant of?
As you are aware, this is hard to answer. Hours worked don't translate well to months, since you often think about things and are engaged when you aren't officially "on the clock". 

Of course the answer also depends on how complete you are allowed to be in reporting. If it is an open ended question, I'd suggest that you just list each activity with both (a) how many months you were engaged and (b) and estimate of how many hours per week (or whatever) you spent over that time.

But if you can create that list you can probably also reduce it to a range of months, something like "8-12 covering different activities at different times". You could use that if you need to give a short description. 

If you need to give a single numeric answer without caveats and some precision is required, just give your best guess based on the above, but be prepared to discuss it in any interview you might have.