What should be the usual content for the {interval} variables in the fast interval markets?

It’s 0-10, 10-20, 20-30, so a string with a dash in between, and the interval is always 10 minutes. The actual end of the interval is before the stated minute; for example, in the 10-20 interval, the market covers the time period of 10:00-19:59, while 20 already belongs to the next market line with the interval 20-30.