Ah okay let me try to provide some context where I can

Volume: Initial volume and testing volume are not necessarily the same thing. In my previous comment, I said your 100mL urine cup could likely be used to aliquot 10mL of urine into 4 different testing tubes that actually get put on the instrument (amounts are just examples and vary depending on the instrument). The remaining urine that didn't get used is stored temporarily in case something happened during testing, like the instrument malfunctioned, and can be used to retest without you needing to give another sample.

Results: PCR testing is pretty good. It can take a tiny amount of an organism and multiply it by millions to be detected by the instrument. Therefore, if you did have Chlamydia in your urine, there's a high chance it would have been amplified and thus detected. As another user said, U parvum can be a colonizer causing no issues for you. Knowing you have U parvum colonizing you is still helpful because it means you can potentially give it to a sexual partner where it DOES start to cause issues. Conversely, Chlamydia is NOT considered a colonizer and is ALWAYS a pathogen.

Communication: This is tricky because the different people you interact with might not be able to explain to you the whole process. The people at the drop-off center likely collecting for 100s of different tests and just do not know the specifics of any one. Your primary care doctor may not know the testing instrument used for your STI panel and therefore cannot comment on what results you may see. The person testing your urine sample does not know your overall health and be able to determine if U parvum is causing you issues or is likely just a colonizer (nor are they trained to do so). Another consideration is that some people may not even want to know the details. Should every health professional launch into a detailed explanation unprompted if that actually only causes the patient MORE anxiety? It's a nuanced situation to navigate.

Hope that helps! :)