I know for a temp to be considered a rise it must go up 0.2 degrees F. But what makes up a drop?

I'm currently in the TWW (10 or 11 dpo depending on if you ask Kindara or FF), and my temp is 98.18 today. Still well above my cover line, but lower that the past two days. I attached my chart so you know what I mean:

So what do you think? Was that a drop? What would you consider a temp drop in the TWW?

Thank you!!!