Hello there,
as simple lines, before appraisals many of your employees might not have same salaries, they might hire based on exp or education or some other reasons, but all they do is same job; so if any employee came to you and ask on appraisal and compare with x salary; ask them a straight question that you enjoy benefit of more salary than him/her for this 1 year; let them enjoy the same for this year; moreover we want to see equal in salary part of everyone; so for people who are less in salary with others, we have given high hike, so people are in average salary, we have given low hike to make consistency among yourselves.
They might not listen your words as mentioned above, but they believe the appraisal happened for not being a wrong performance or poor feedback from seniors. at least that gave them a positive note on their work