Looking at today's sieving stats , 30 candidates were eliminated in the range 3M<n<4M, also current candidates remaining in that range (excluding PRP) are 35995. There are currently 2809 PRP tests pending, almost all of them in this n range.
(2809 * 30)/35995 = 2.34
Which means that given even distribution, 2 PRP tests are currently being performed for k/n pairs for which factors are now known.
Again, given even distribution, each of those tests will be 50% complete. Thus about one whole PRP testing effort being lost every day.