BMR!!! am i 100%......

i know you must be really annoyed by people asking the same question but to make sure i get this a 100%......
My bmr = 1400 calories
I burned = 250 calories
I ate = 1700 calories
Take away my bmr from 1700 = 300 calories
Take away my burned 250 calories = 50 calories
Total in my body 50 calories is that right??? Have i finally got it???
Just to let you know i calculated this on a normal day, and if i am living off 50 calories that cant be good for me right?Do i need to change how much im eating?
Thanks for reading it =) xxx

soooo am i getting this right now then?

anddd if i go over my calories like the 50 calories just will they eventually add up to 3500 and gain a pound???

thanks again x