Ovulation dips are not that common. There's almost always some range` of temperatures in the pre-shift 6, but that doesn't tell you exactly what day ovulation happens. Technically, it can be with a few days of your temperature rise or of Peak day. I would count the first day that your temperature is above the 6 temperatures before it as 1 DPO. Alternately, you can count the number of days after Peak day as your LP. Sometimes, you get different numbers because we can't pinpoint ovulation without an ultrasound. That is why we use rules that have us waiting for a few days after the start of the temperature rise and after Peak day before we can safely assume that we are infertile.
It is not uncommon to have higher than average temperatures during your period. Estrogen is what prepares the follicle for ovulation and lowers your temperature. If you don't have much estrogen yet because you aren't getting ready to ovulate yet, it's not abnormal to have temperatures above your CL during your period. It is normal, however, to have a sudden drop in temperature at the start of your period. This is one of the signs that it is a true period and not bleeding during pregnancy. Your temperature may go right back up the next day, but if it drops on the first day of your period, that is a sign that you are not likely pregnant.
9 days is considered to be possibly a fertile LP. 8 days is probably not, and 10 days is almost certainly fertile. 9 days is marginal. It may be quite possible for the embryo to implant and make enough HCG to stop your period by 9 days. It's hard to study because when a woman gets pregnant, we don't know how long her LP would have been. You can't project that your LP will be the same as it was the last cycle, so if you have a 9 day LP last cycle, you might have a 10 or 11 day LP this cycle. I've heard of people having extremely short LP's, like 3-5 days and then getting pregnant the next cycle. There's no way a 3-5 day LP would be fertile, but it is quite possible for the LP to suddenly jump from impossibly infertile to fertile in one cycle. Assuming that you can't get pregnant because of a short LP is not a very effective means of family planning.