It does look like you've over exposed the step tablet, although it looks like you got results good enough to work with. I am a little concerned about the second Fb+f reading if I am correct in assuming that your Fb+f readings are 0.16, 0.13, 0.16, 0.19, 0.20? Film base plus fog doesn't decrease with increased processing, and the drop is too big to just be attributed to densitometer accuracy. As the next step (31) appears to be consistent with the data from the other test wedges it probably isn't operator error either. The 0.03 density drop for the Fb+f could be pointing to an error in the testing procedure. Don't discount the possibility that it might not be the one with the error. If there is a problem, perhaps it is with the other tests.