From Unofficial BOINC Wiki
Credit is "Claimed" upon completion of a specific Work Unit. When that Work Unit's results are returned to the Data Server the BOINC Client Software submits a claim for the amount of Credit you should be granted when confirming Results are returned by another Participant in that project who also processed that same Work Unit.
In the instance where you are returning a result that confirms another result already returned; some, or all, of your Claimed Credit will be quickly turned into Total Credit. This does not happen immediately because of the time it takes the back-end systems to perform all of its tasks.
The basic formula for calculating Claimed Credit is:
claimed credit = ([whetstone]+[dhrystone]) * wu_cpu_time_in_sec / 1728000
With my computer EQ-1, I have, for example:
Measured floating point speed 1394.01 million ops/sec Measured integer speed 2630.73 million ops/sec ------- Total: 4024.74
37,698.15625 * 4,024.74000 ----------------- 151,725,277.38562 Ã· 1,728,000 ----------------- 87.80397
Which, when rounded gives the displayed Claimed Credit value 87.80 as expected. Note that there is a more precise value shown on the "Result" Page (in this case it was: 87.8039391846125 for what that is worth).
6,354.078125 * 4,024.740000 ------------------ 25,573,512.372689 Ã· 1,728,000 ------------------ 14.799486
Which, once again, when rounded gives the displayed Claimed Credit value 14.80 as expected. Note that there is a more precise value shown on the Result page (in this case it was: 14.799486326788 again, for what that is worth).
For whatever reason, the two examples came up with a value of "X.80" and that is just an artifact. So, don't read anything into that!
Note: There is an additional refinement in that the Project can determine and specify the ratio of Floating Point to Integer mathmatics with a fraction that is used to scale the benchmark multipliers, with the variable "a" representing the scaling fraction, gives us:
claimed credit = ( a * whetstone + (1 - a) * dhrystone) * wu_cpu_time_in_sec / 1728000