Depending on the test kit you are using, non-chlorine shock will register as CC. 2 ounces of Renew (which is 33% MPS) in 250 gallons is equivalent in oxidizing power (and in how it registers on chlorine tests) to 9.2 ppm chlorine. Did you measure the water very soon after you added the Renew? If so, then it may be registering as FC on your chlorine test.
Eventually, the MPS will drop, but if you want to use chlorine and MPS you might consider getting a better test kit where you can use an MPS interference remover. The
Taylor K-1515-A is a FAS-DPD chlorine test you can use along with the
Taylor K-2042 MPS interference remover. Instead of the 1515, you can get the
Taylor K-2006 if you do not already have a good complete test kit. If you already have this kit, then just get the 2042 interference remover.