For me, CRON is pretty easy to define.
I take my Basal Metabolic Rate and add calories for my activity level. Then I subtract 10% to 40% of the calories to arrive at a Calorie Restricted range of calories. You can use the CRON Calculator or other online tools to determine this quickly and easily. I personally aim for about 25%.
If you're not within that range... in my opinion, you're not following CRON.
I should also note that I would not allow my weight to drop below a BMI of 16. I would move to more of a maintenance caloric intake at that point as the I believe health gets worse at or below this BMI for males.
What really gets me though is people who say they are CRON followers but regularly take in large amounts of calories nowhere near that range. For small periods of time, I can understand that. However, on a regular basis - you are not following CRON and you likely need to face up to that and stop calling it CRON.