The Revenue Recognition export will only show 12 columns of months at one time. There will be a column for each month after the current month. What this means is that every month, a new month will appear in the export as time progresses. Let's say it is currently August 2020, so you will only see August 2020 and 11 months after that month.
On September 2020, you will see September 2020 as the current month, and then 11 months after that month.
Similarly, in October, you will see October 2020 as the current month, and then 11 months after that month.