Magic of finding the hidden number

Step no 1: Think about 4 digit number less than 8999 without telling me or showing to my camera.
Step no 2: Add each digit individually. For eg, if you have chosen 2341 then add 2 + 3 + 4 + 1 and find the answer.
Step no 3: Subtract answer from step no 2 from original number chosen in step no 1. In this case it will be 2341 – 10 = 2331
Step no 4: Hide one digit from the final answer and enter remaining 3 digits in the box. In this case for eg you can hide 3 and tell remaining digits 2, 3 and 1.Then, I will tell you the number which you have hidden from me
Or
Step no 1: Think about 4 digit number with all 4 digits different without telling me or showing to my camera.
Step no 2: Reverse 4 digits to form new number. For eg, if you have chosen 2348 then new number would be 8432.
Step no 3: Subtract the small number from the large number out of your original number and reversed number. In this case it will be 8432 – 2348 = 6084.
Step no 4: Hide one digit from the final answer and enter the remaining 3 digits in the box. In this case for eg you can hide 6 and tell remaining digits 0, 8 and 4. Then, I will tell you the number which you have hidden from me.

Hide one digit and enter a remaining three digits: Find the hidden number