11am is not the time to test - you need to test at 8am, fasting.
As LM pointed out, the tests differ, I can tell you why. There are a few cortisol tests, blood, urine and saliva. Blood tests check for serum cortisol. Urine and saliva check for free cortisol.
The blood and saliva tests are point in time, that is, if you are not high or low at the exact time of the test, that is it.
The 24 hour urine test is an average.