I wouldn't have done that, .008 is such an insignificant amount. Plus more than likely the og was dead on.
It's a pretty common issue for ANYONE using extract and then topping off with water (and that includes partial mashes) to have an error in reading the OG...In fact, it is actually nearly impossible to mix the wort and the top off water in a way to get an accurate OG reading...
Brewers get a low reading if they get more of the top off water than the wort, conversely they get a number over if they grabbed more of the extract than the top off water in their sample.
Like i said it is pretty common.
When I am doing an extract with grain recipe I make sure to stir for a minimum of 5 minutes (whipping up a froth to aerate as well) before I draw a grav sample and pitch my yeast....It really is an effort to integrate the wort with the top off water...This is a fairly common new brewer issue we get on here...unless you under or over topped off or the final volume for the kit was 5 gallons and you topped off to 5.5, then the issue, sorry to say, is "operator error"
it doesn't matter what your reading was.....the "real reading" in an extract batch is what it said it would be in the recipe or beersmith....Whether or not you mixed it up enough before you took the reading it mixed itself up fine during fermentation.
So unless you had a final volume a gallon or so higher than 5 gallons....you recipe will be fine and at the OG it was supposed to be,
I bet your OG is EXACTLY what it is supposed to be.
And during fermentation the wort and water will mix up just fine on it's own.
Next time, just relx and don't try to "fix" anything that might not be broken.