CDC FluVu.The number comes from their weekly chart for the deaths in each flu season. If you go to that chart with all the colored sign waves, there is a link for the data which is in an Excel spread sheet. Add up 2020 flu season weeks 1-11 and you will get 4,944. The usual flu season is week 40 of one year coupled with week 10-39 of the next year. The 2019-2020 year will be probably double this number but it won’t get up to the 24,000 estimate. It never does. The worst season was 2017-18 and the total was 15,900 or so.
I don’t know how the CDC gets their estimates for deaths per year. The data above comes from 2 sources they cite in the verbiage, which the CDC site is full of.
https://gis.cdc.gov/grasp/fluview/mortality.html
You have to add in the pneumonia deaths (38,001 for weeks 1-11) to the flu deaths to get to the total of 42,945.
That is what the CDC does.
Here's the CDC explaining (or trying to justify) its mortality numbers for the flu: How the CDC Estimates Influenza-Associated Deaths
The CDC's position is that deaths from flu are underreported, so CDC estimates a much higher number.
In other words, those weekly numbers in that file are exaggerated estimates. Very few death certificates list "flu" as the cause.
For an idea on just how much the CDC exaggerates the number of deaths from flu, click on this 2010 National Vital Statistics report and go to page 39. That chart indicates that 500 people died from the flu that year (as per their death certificates), whereas almost 50,000 died of pneumonia.
Nowadays, CDC isn't even telling us how many people died of the flu (as per their death certificates). It just combines the number of flu and pneumonia deaths to make the number look much larger.