Confused😩

Cerys • Workaholic💵 ttc #1👣 ghanian🇬🇭
 I tested at 12dpo (if my recording is correct) and the test was negative,however glow predicts that af should of come today although af normally turns up a few days before glow predicts (started February 14th instead of 17th) I'm very boated and it's obvious to see, but if the test showed up negative at 12 DPO what could the cause for this be?