Claimed credit is based on the benchmarks your computer runs when you set up the BOINC client. The factors that affect it include IntegerOps/second, FloatingPointOps/second, and so forth.

For Rosetta, granted credit is based on the number of models/decoys that your computer actually builds during the time it is running the task, irrespective of the amount of time it takes to build each model.

The very first person to report a particular type of task gets exactly the same granted credit as claimed credit.

For each person who reports after the first, the granted credit is a running average of all of the claimed credits previously.

The following is my understanding of how the system works. I could be wrong. I humbly submit to correction by anyone better informed than myself.

Example:

The first person to report completes 10 models and claims 100 credits. They get exactly what they claimed. Those models are worth 10 credits each, regardless of how long it took to make them.

The second person to report completes 8 models and claims 170 credits. They get 80 credits, because the models were worth 10 credits each when they reported. However, the models will be worth a little more to the next person.

At this point, 18 models have been completed and 270 credits have been claimed. The models are now worth 15 credits each.

The third person to report completes 12 models and claims 90 credits. They get 180 credits, because models were worth 15 credits each when they reported. However, the models will be worth a little less to the next person.

At this point, 30 models have been completed and 360 credits have been claimed. The models are now worth 12 credits each.

And so on...

Again, I remind you that the above is my understanding of the process, and my understanding may be flawed.