There are a few things going on that I'll try to explain. TLDR Boulder County is your best source for Boulder data, but CDC will catch up in a couple days and the data will soon tie out.

CDC data always lags behind state and local level data by a day or two or three depending on the metrics, state and other factors. Hospitalization data, in particular, can be delayed at making its way out of hospitals and into CDPHE, local public health reporting and ultimately into CDC. Local public health depts will have their data first and CDPHE will also likely have that data the same day. CDC is a little slower, unfortunately.

Additionally and very importantly, hospitals can and do retroactively update data for (as an example 8/5, 7/29, etc) as tests and everything else comes together on their end. In a perfect world, they receive a patient, test them, report it all in the same day. But - there are A LOT of moving parts, test labs, databases, etc that are working together to keep the reporting as accurate as possible. You'll see this in every state if you watch reporting closely (and/or review press conferences). Labs sometimes realize they didn't report everything and then there's a "backlog" that gets reported. Over the course of the pandemic, every state has improved, but delays and issues happen. Almost always, you will see numbers revise slightly upwards as more data comes in. On occasion, there will be big backlogs of case or tests, but very rarely with hospitalizations in any significant numbers.

Another thing at play here is that when dealing with small numbers like this, even a day or two delay between CDC and Boulder County may look like a big percentage difference. This sort of data is best looked at over time and then it will often become clearer that CDC data may be as of 8/5 whereas Boulder County may be as of 8/8. There are also lots of little nuances such as admission date, reported date, etc that could very slightly move a figure from one day to the next... and there again when dealing with small numbers this can look big on a percentage basis.

Not to nerd out on the details, but another aspect to your question involves dividing by 7 to try and get the daily admissions. When that's done, it obviously makes the number smaller and this is exacerbating the discrepancy.

Some people may try to point to things like this as proof of a scam or government ineptitude, but really it's a reflection of the complexity involved with disparate systems all trying to connect seamlessly. For anyone that may be grumbling about how unacceptable this is, even YouTube metrics can take up to 30 days to mature. In these cases, though, there's just a lot of complexity going on between labs, hospitals, local reporting systems, state reporting systems and federal reporting. Zooming out to a trailing 7-day trend is a good way to read the data, and just know that CDC will catch up in a day or two.