Best case you’re transforming 10^6 cells and you expect 20 of them to take up the DNA. Worse case it could be 10^11 cells for a strain of bacteria that doesn’t

Best case you’re transforming 10^6 cells and you expect 20 of them to take up the DNA. Worse case it could be 10^11 cells for a strain of bacteria that doesn’t transform well. You would have to look at a lot of colonies to find the one that transformed.