Basically, if you want a 1g of 5x extract... You take 5g of dried leaf, let it sit in acetone for a few minutes, then evaporate it down onto 1g of regular leaf... 1x + 5x = 6x (but, you need to account for losses, so it's really "5x").
This works for 10x... 10g of dried leaf in acetone evaporated onto 1g of leaf...
Takes a *lot* of leaf... but, it will work.
Ya, this method will work for un-standardized reason upon SD leaf up to 10X SD. However, the acetone extract would need to be cleaned with a NP solvent like naphtha to get a stronger product then that. Pure SD reason made using acetone tends to be 20X. In other words, the 15X on up have had the extract cleaned like that.