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NOTES: Data presented in this table are based on all complete death records received and processed by the Centers for Disease Control and Prevention’s National Center for Health Statistics (NCHS) as of March 17, 2016. Data for 2008 through 2014 are final data, while 2015 data are provisional. Due to the nature of provisional data, numbers are subject to change as additional death records are received. Influenza season is defined as early October through mid-May. Influenza and pneumonia deaths are defined as deaths with codes J09–J11 (any listed cause) and J12–18 (listed anywhere without influenza also listed), respectively, in the International Classification of Diseases, Tenth Revision. SOURCE: CDC/NCHS, National Vital Statistics System, 2008–2015.
It's not one year. The document covers 7 years. The pneumonia range is 126k to 138k. It's explicitely listed as "death records" and the source is given.
Here's the data I was quoting: https://www.cdc.gov/flu/about/burden/index.html
Here is 2017 from 2016 (which I believe is basically the 2016-2017 calendar year) national vital statistic report: https://www.cdc.gov/nchs/data/nvsr/nvsr68/nvsr68_09-508.pdf
If you scroll down to Table B you can see that ~2,800,000 people died, influenza and pneumonia account for 55,000 deaths. This is more than that 33,000 cases of reported influenza because not all pneumonia is caused by the flu.
The data in your link is very strange in that it implies a rate of 10% of all deaths is by pneumonia, rather than the ~2% in roughly everything else I can find on the topic. I wonder if we are losing some context here?
Here is another mortality report. Just search for pneumonia: https://www.cdc.gov/nchs/data/nvsr/nvsr68/nvsr68_09_tables-5...
Literally nothing I can find on the CDC's website matches up with the data on that report so I'm at a loss what's going on with it. It's too bad there is no text because I think we're missing something.