Paid Amount vs Transaction Amount in Analytics

Hi, all-

I see in the documentation for the finance cube the definitions for ticket paid amount and transaction amount, but I am wondering why these would be different?

Can anyone please elaborate why I might see a difference between the two?

Thanks!

Rachel

https://www.tessituranetwork.com/Help_System/Tessitura.htm#Tessitura%20Analytics/Data%20Dictionary/Finance%20Cube.htm

Ticket Paid Amount

The sum of all purchase, refund, and change transaction amounts for a ticket (SLI).  
Ticket Purchase Amount The amount from purchase transactions for a ticket (SLI). This value excludes amounts from refund and change transactions. Added v15.1.10
Ticket Refund Amount The amount from refund transactions for a ticket (SLI), formatted as a positive number. This value excludes amounts from purchase and change transactions (such as when applying the refund amount directly to other tickets or contributions). Added v15.1.10
Transaction Amount The total transaction amount.