Why is glow telling me to take another opk, after a positive?

I use them intermittently so I don't know all the ins and outs (same with bbt)..but I had a very positive opk saturday. I logged it and glow is telling me to take one again today? This seems kind of a waste to me. I've only gotten one other positive but found there was no reason to keep testing after. Thanks in advance. Good luck and baby dust to all!