How is my chart looking for ovulation? New to bbt..Blue triangle??

Brianna • Mommy to a girl born 9/12/2008.😇 10/26/18. MMC 5/20/19 🤰🏼 🌈 due in April 2020!

First month temping. I switched to the himama fertility monitor on cd 17. I had positive opk on cd 18 and 19th. Big jump this morning but it’s all still confusing to me. Also anyone know what the blue triangle means?