alt Hacker NewsGeekbench multi-core has been a single-task benchmark since version 6. The multi-core / single-core score ratio is supposed to tell how much you will benefit on the average when you use all available CPU cores. Some tasks parallelize better, while others have bottlenecks that prevent effective parallelization. For every CPU, the ratio is well below the nominal speedup you can get under ideal circumstances.
Note that Geekbench 7 no longer runs the same subtests in multi-core mode as in single-core mode, so any ratio calculated from the overall scores instead of from the individual subtests is misleading. There are a lot of subtests that it only runs in single-core mode and omits from the multi-core tests, seemingly to placate the critics that didn't like the inclusion of poorly-scaling tests in the multi-core mode. It's not as dumb as the Geekbench 5 strategy of just running N independent copies of the test, but it does seem like a dumb change to me.