How many days after no period will digital be effective?

Adriana • Mama of three 👦🏻👧🏻👶🏻 expecting number 4 🤪🤪 in May 2020 🤰🏻

Hi. I’ve taken two test kinda maybe see a faint line. I looked at them way later and see if more but I know that doesn’t really mean anything. Took a digital says not pregnant. I’m 6 days late. Just looking for some knowledge on the digital test. Thanks ladies