Quick question about BC and period!

Hi! So I was just curious that when logging for my period - when I see the spotting is that when I log that my period started and when I end it do I wait for there to be brown blood or absolutely nothing left?

Also I’m just now starting birth control and I believe my period is at its end today but the packet says first pill on a Sunday. So do I do it tonight cause my period ended or on Sunday?

Thanks for helping me out :)