It clearly says in the documentation that point in time backups expects number of milliseconds. But the example shows the UNIX timestamp in seconds.
Based on my own usage of the CLI, I actually think the example is correct and the documentation/naming of the option is wrong. The atlas backup restore start pointInTime does actually expect the epoch to be in seconds.
Just to double check, can you provide the atlas cli version you’re using and the command you used to get this error: Please redact the specific project ID’s and any other sensitive information before posting here
There is a ticket now logged for this which I am monitoring and will update here when the appropriate changes are made.