Very interesting subject. Day before yesterday I changed seals and belt on a daughter's 1990 244 first time since purchased about 20K miles and 18 months ago. I did not have records, so this bit of preventive maintenance was potentially overdue. The performance was never questioned, nor do I remember it being doggy test driving it, yet the last guy who did the timing belt had the crank advanced one tooth. He even used green paint to mark the incorrect position on the bearing carrier and the inner belt guide.

So, I conclude two things: One, more than one professional has had trouble identifying the reference marks, and two, the cam timing can be one tooth retarded and not elicit complaints from my #1 daughter. While looking at a photo of this, I see that I botched the seal install somehow, so I'm compelled to re-do the job too. Then, I'm going to count teeth so I can learn just how many degrees a tooth makes, and answer the planetary alignment mystery puzzler "how many engine revs before the white lines on a new timing belt match the marks again".
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Art Benstein near Baltimore