Enter the dose you want of one peptide and see what the rest of the blend gives you.
You can't dose one peptide in a blend on its own — you draw a volume and get all of them, in whatever ratio the vial was made at. So pick the one you actually dose to, enter how much you want, and this works out the draw and what the others come along at.
Read these off your vial or the product page. Vendors write blends up inconsistently — some list each peptide, some only the total — so use the numbers for the vial in your hand.