Too late?

So my calendar is predicting AF to arrive tomorrow. Yesterday I started spotting, I’m around 12-13dpo (I believe if I calculated correctly) I got my solid smiley on the 8th, & if ovulation happens 12-24 hours from then, I believe I’m around that! Anyway, I started spotting very light brown yesterday, is it too late to be considered IB? I found a chart online that shows the differences and of course I’ve talked myself into believing it may be IB. Am I too late? I know this could also be AF also because some women don’t experience IB at all. Just looking for opinions!