Thanks Moon Palace
In the rest of the document I have translated 'rebut' as scrap. This paint possibly isnt up to standard or is the result of test batches on the paint line.
I really dont understand the 'top rebut'!
Can we translate 'top' as rate/frequency? Even so, I'm not sure it makes sense!
If we're talking of a continuous process in a production line, it could be the first liters (or whatever quantity) produced on the line, that is usually discarded. But this is as wild a guess as it goes here!