Calculating total calories burned per day

When I calculate my burn using the formula on Opex website:
BMR = 1,804
TEF (thermic effect of feeding) add 180
EEE (exercise) add 400
NEAT (non exercise activity) add 250
Total = 2,634
However the app adds to BMR for me today 793 for exercise and 840 for activity for a total of 3,437. The Opex calculator says the max for exercise is usually 500 and for activity is 500. How can your app give me so much more? Big difference.
Thanks

PS - the website for calculator is: https://www.opexfit.com/blog/how-to-calculate-tdee-total-daily-energy-expenditure