If, somehow, we could tag each molecule of P & K in the fertilizer and the free stuff in the soil, you would find the fertilizer molecules would be available to the plant much later. If there were a thousand of these "fertilizers", and they were lined-up waiting for ingestion by the plant, they would, for illustration purposes, be 101,000, 101,001, 101,002....
The first hundred thousand are already in solution in the soil. That's what your soil test measured. Next year, when you again sample, the test results will be higher because the things that go on in the soil to break free potassium molecules will have had time to work on your contribution.
That didn't answer your question. Which is, do it now.