Book2.xlsx

I'm trying to get the difference between the first value and the last value, and add 1 to the result. This is what I tried to do:

B2: = (RIGHT(A2,1)-LEFT(A2,1))+1

This works fine if all the values are single digit, but if the last value is two digits, then it doesn't give the correct result.

Is there a better way of writing this formula which works fine both for single and double digits? please. thanks

On the link to excel file above, there are some data and expected results, and how the expected results obtained.