PLEASE REPSOND help distinguishing cycle day

Okay so I'm suppose to start taking Letrozole on cycle day 3-7. I had pink spotting yesterday morning/afternoon. Then light pink bleeding at 10pm. This morning I also had light pink bleeding and I used a tampon and when I took it out I saw red and brown blood not a lot still very light. So do I count yesterday as cycle day 1 or today as cycle day 1?