First of all, let me remark that I am not sure whether or not this question is on-topic here; if it is not, any hint as to where it should be posted instead is welcome! (One option would be to ask in an "English Language" community; however, I guess a similar ambiguity exists in many other languages as well, so it is more a math issue than a language one.)
I am wondering whether there is a "standard" interpretation of the term "average" in a sentence such as "On average, customers were refunded $x$ percent of their expenses". I can think of at least two different interpretations which I'll illustrate with the following example:
Assume that customer A spends 500 and is refunded 50, so his refund is 10%. Customer B spends 2000 and is refunded 100, which is 5%.
By the first interpretation, the average refund would be $(10\% + 5\%)/2 = 7.5\%$.
For the second interpretation, we compute the total expenses ($500 + 2000 = 2500$) and the total refunds ($50 + 100 = 150$), which is $6\%$ of the total cost, so this value could also be interpreted as the average refund.
Would you say in this scenario that on average, customers were refunded $7.5$ percent or $6$ percent of their costs?
Let's take an example : I go to a hotel for a one night stay, and order my dinner which is available on 25% discount. Say, dinner costs me 100. Due to 25% discount I end up paying him 75. Now, in the morning I get 50% discount on my breakfast and for 100 , I end up paying 50. So the total money I paid on $200 bill is 50+25=75. Taking the second case,now if I add up the discounts , I get 50%+25% = 75% discount on (adding up the total bill value) 100+100=200. This amounts to a total of 150 discount and I should pay only 50. This is a wrong way to look at it. You cannot just first add up the discount percentages and 'apply' them on the whole. You need to compute the percentages separately and then add.Now, with this background I hope you will be able to answer.