It is unrealistic to project a quantified mindset onto early Buddhists. They didn't have paper to write on. They didn't have writing. Without writing, math must have been rather limited, let alone mathematical thinking. Later on, Buddhist universities developed logic, which is a sort of propositional math. There were whole manuals for Buddhist logic exercises. In Mahayana, there are sutras with chapters that discuss powers of 10 and extremely large numbers (Avatamsaka is one).
My personal thoughts on the matter
I recently started using beeminder.com to track my meditation. I give my self a point a day for meditating. If I'm derailed on my goal, I pay a small fine.
The most measurable things are going to be inputs, e.g. minutes meditating. The outputs might be measurable using techniques of modern psychologists, by say by writing 20 similar questions that elicit if you are exhibiting this or that quality. Adding up the "yes"es is a score of the outputs of contemplation. Even in psychology, these metrics are controversial as to if they really measure what they purport to measure.
In the universe of all Buddhist practices, some are more measurable that others (keep in mind, I'm not promoting any of these, just making a comment on what Buddhist broadly defined do that is quantifiable)
- Chanting- # of matra repetitions. Chanting is noisy meditation, usually counted with mala beads.
- Prostrations- # of prostrations. Prostrations are like meditation, but with constant motion
- Infractions of precepts - Even early Buddhists were expected to list their infractions at Uposotha.
- Meditation time. I know monks used to use incense sticks as timers, so they'd meditate for n incense sticks.
- Meritable acts. In Mahayana texts there are many rhetorical flourishes that involve merit accounting, such as "you can transfer 1/8 of the merit of a good act to your deceased kin.", or the merit of doing this is more than the merit of doing that (i.e. a measure that is rankable) The math geek in me wishes they'd fully developed the system, but AFAIK, it wasn't a fully developed system. It sort of reminds me of the Boy Scouts effort to do one good deed a day. Vajrayana also has many practices that are done n times, with merit accruing for each, such as turning prayer wheels, making flags, etc.