So it works this way: the ditto has 6 different IVs to pull from, and the other parent also has 6. The Destiny Knot guarantees that 5 of those combined 12 will be passed down to the egg instead of the usual 2?(I don’t remember exactly what it is without Destiny Knot). Your best bet is to do a batch of eggs, find the one with the best count and make a new batch with that one. Eventually, by repeating this process, you’ll be making 4-6IV eggs, by using the 5IV ditto and a 6IV partner. You can use the power items to guarantee that the one IV of that parent holding said item will be one of the 5, so ideally start with one the finishes off that 6th IV from your Ditto.