waverless I wonder about the % positive too. There's an article here that is quite helpful.
But we know through ONS testing of random people (ie not just symptomatic people) that in scotland our prevalence is less than 1% overall. So ideally the nhs/ gov testing programme should be getting something like that percentage (or a little bit higher because we wouldn't necessarily test completely asymptomatic people).
But as we aren't, it suggests that the number of tests we are doing isn't enough to capture everyone (with symptoms) with the virus, meaning some people don't know they have it or aren't coming forward for testing, and we aren't getting their contacts, meaning we can't prevent them from spreading it further. Scotland does seem to be testing less per head than the rest of the UK, the last I saw.
I know some people are tested routinely through work, but not sure if those figures are included in the %positive figure. It does seem a bit counterintuitive to increase the number of people eligible for a test, just to bring the % positive down, though. But that would mean more "non-typical" cases without the 3 key symptoms were caught. Whether or not that would actually lead to a decrease in hospitalisations or deaths is uncertain, though. And it would definitely result in more people having to self isolate etc...