When I make NET e-juice I usually only put 3% NET in my liquid. Put in a little bit of graham cracker, and hazelnut or acetyl pyrazine.
Assuming you've filtered out any remaining particles, try a micro-mix to get a gauge of its potency.
1 drop extract to 19 drops base will let you taste it at 5%, which will probably be too much but homebrew extracts aren't always consistent. 5% should let you know how strong it is even if it's a bit weak, then you can do a 10 ml batch with more confidence in how strong it will be.
If its so strong that you need to keep it under 2-3% you may want to dilute it so its easier to work with, but that's up to you, maybe you want something you can put 2 drops of into a 30ml of base and call it done...
Just realized you're talking alcohol extract (I think).
This is a PG soak :) steeped it about a month, and ran an equal part clear pg through after the first filtering, so its roughly 50% strength.
Its tasty, but gunking coils like mad at full pg mix. Gonna run it through several more filter cycles and possibly add some VG if filtering fixes gunk issues.