The Bar Counts as Weight
An empty standard barbell already weighs 45 lb (20 kg).
That's not nothing — for many people the bar alone is a real warm-up.
Every weight the app shows you is the total on the bar, bar included. If the app says 95 lb, that's the 45 lb bar plus 50 lb of plates — 25 lb on each side.
You never add the bar on top of the number; it's already in there.
If you're brand new and the bar by itself is plenty, that's a fine place to start. 5/3/1 adds weight every cycle, so starting light is the plan working, not a problem.