A moderately active 50 lb dog needs roughly 1,100 kcal per day. Following the vet 10% rule, that means treats should stay under about 110 kcal/day.
The exact treat count depends on calories per treat. Most small training treats are 5–10 kcal each, so a 50 lb dog can have about 10–20 treats per day — fewer if you also give chews, dental sticks, or table scraps.
Treats should never replace meals. The remaining 90% of daily calories should come from a complete, balanced diet to support healthy weight and nutrition.