Forty-eight hours is
$1.
Your issue here is that your manager was symptomatic on Monday, which should allow you to self-isolate, BUT your manager would have had to self identify their symptoms as possible COVID-19 and not something else. For example, when I got my flu shot this year, they told me if I had symptoms to get a COVID test just to be safe. If I was your manager, I could chalk my symptoms up to the fact that I got a flu shot since the COVID coach only asks you if you’re experiencing any unexplained symptoms.
Now that they have a positive test, they can enforce the 48 hour rule.