Menstrual cycle data

A menstrual cycle is count (by agreement) from the first day of the onset of menstrual bleeding (this is considered as the first day of the cycle, as a whole) to the last day of one cycle, which is the day before the start of the next menstrual bleeding (bleeding days are colloquially called “the period”).

Given the information you provided about your last menstrual period (LMP), which started on October 18th and the information about the length of your whole menstrual cycle (as explained above), it is understood that you get your periodical bleeding regularly, every 30 days. (The cycle length is considered normal between 21 and 35 days).

So you might expect your next period to begin by November 17th, plus/minus 1-2 days, if the cycle is regular.
Bleeding length is considered normal from 3-7 days.