Math Question

Ok here is the way I think the math should go on my Raspberry Blonde.
take the OG...say 1.058
then take a sg after it's stopped dropping...say 1.010
then add Berries and take another sg ...say 1.018
then a fg after secondary ....say 1.012
then the math would be 58-10= 48 points plus 18-12 for a total of 54 points the use my handy BS ABV calc using an OG of 1.058 and a FG of 1.004 to get an ABV of 7.1%
so how close will I be?

You should be pretty close, but you may actually get some additional fermentables from the meat of the fruit that hasn't come out when you take the SG at 1.018. 

thanks