EDIT: Nevermind, can disregard the paragraph to follow. i've run three tests and got three codes but all are same code so no worries :) Apologies BlueMooner for sending you a redeemed code.
i ran the test a second time some hours late and got a second code. If it helps to test at different times of day i will. But had figured that it'd be only one code per person. Can give them away but don't want to deter anyone else from participating. Does it cause any accounting error or other hassle if users get a bunch of codes but don't use them? And if we give them out after the test concludes, is that a notable hit to finances?