For most women, it's around four tablespoons, but for some, it's as much as a cup. Sometimes the blood is red, sometimes it's brown, sometimes it's streaky, sometimes it's got some darker bits in it. Every girl is different. You heard right. Or if you have more questions regarding fertility and your period, talk to your doctor.
Menstrual cramps vary a lot in intensity, from woman to woman and even from cycle to cycle.
You can also get your mother, your sister, or a friend to rub your stomach, which can be very gratifying. It's probably just that a heavy flow, which can often happen the first day or two. For some girls, a heavy flow is normal. If you have a prolonged heavy flow, you should check with your doctor. No, do your normal activities.