Nothing to worry about!
First of all those mixing cup measurement can be off 1-3%, worse i ever saw was one brand was 5% off and only reason i knew that is the warehouse was out of the brand I buy case lots of and they sent me there warehouse brand and all my gel testing was wrong.
But most important, SPI OVERFILLS all containers, the reason for this is going by weight per gallon a lot of products would be up to 2-4 inches below what looks full in the gallon or quart.
I never want anyone to call me and say my gallon or quart is short of material, so with this said, its not uncommon to have extra activator or extra clear or epoxy left over from your mix.
The only product that is now an exact fill is the 700 and we changed that about 3 months ago as overfilling the plastic jugs they expand and we have always had a problem with the cases bulging.
One of our new guys figured this out and programed the filling machine to do a full gallon and I was not advised until after the 300 gallons was packaged but the cases looked so good for a change we left them that way. I estimate this costs us an extra 6-10% of our proffit depending on product to overfill but I chose to live with it and the only stupid bean counter I have to answer to is me.