Hi there and welcome.
I assume you are referring to Account certificate at https://www.primegrid.com/cert1.php
BOINC credit, or it's units in Cobblestones, are units of performace.
t is a way to compare how much work each participant or computer has provided.
A BOINC project gives you credit for the computations your computers perform for it. BOINC's unit of credit, the Cobblestone (named after Jeff Cobb of SETI@home), is 1/200 day of CPU time on a reference computer that does 1,000 MFLOPS based on the Whetstone benchmark
Here on primegrid, we also have Badges for each respective subproject that represent how much work was done.
Badge score: 1*1 + 5*1 + 8*3 + 9*11 + 10*1 + 11*1 + 12*3 = 186