An adult period can see anywhere between 5 ml - 80 ml of blood leave your body over an 8 day period.
The heaviest days of menstrual bleeding are usually at the beginning of your cycle (around day 1 and 2). During which you may notice clots in your menstrual fluid, which is very normal. The colour of your menstruation may also change as you progress through your period, with bright red blood being more common as flow is heavy, and darker shades when your flow approaches the end of your period.
Adolescent periods can produce the same volume as an adult period, but are usually much lighter.
It’s common for cycles to be somewhat irregular for a few years after your first period. As you progress through adolescence, period amounts and cycles become more regular, but may still be somewhat variable.