Best selling sort does not work if you change your order code

[artpress]

I am using the Spotlight theme. I ordered from my own store to test it out. The item I ordered showed up in the Best selling collection. The order code is #GOM1001. I changed it to GOMUGS****. Three customers ordered. Their orders never showed up in the best selling collection. The list remains the same. Any ideas where I can edit the code that handles best selling sorting so I can look into it? Thanks.