Bfp but confusion with frer digi?

I got my bfp today (10dpo) with dollar store first signal brand and went out and spent $13 on a frer line test that also came with a frer digital. Well took the line test first and immediately came back positive (!!!!) but I took the digi using the same urine and it came back with a “no”. Anyone else have this happen? Are frer digis not as sensitive, and also why sell them with “6 days sooner” advertised? I have had two chemical pregnancies this year so I am hoping this bean sticks but that digi scared me.