I found this: Vectors are priced in 4 categories depending on the type of illustration, design and license option. Note: Not all files have Expanded license options. 1 Credit = $USD1.
1 credit Standard license or 25 with Expanded license
3 credit Standard license or 50 with Expanded license
5 credits Standard license or 75 with Expanded license
10 credits Standard license or 100 with Expanded license
Your sale is probably "25 with Expanded license" - (25% out of 25 USD is 6.25)
I would like to know where rejected files at VectorStock go and see reason of rejection. This site is bit confusing.