bbt adjusting

Because of my work schedule some days I can sleep in till 8am and other days I need to be up at 530am.

So how should I even chart? Bbt at 530am or bbt at 8am? *Note: when I first started charting which was a few days ago I started with 8am so should I adjust the 530am one to match the 8am and just write down both numbers just in case? Thanks!