Why does the cat command display all the content?

[yanzhang920817]

I have a question about abnormal cat commands on stackexchange.
I am customizing a Linux system with a kernel of 6.4.0, and I have notified a strict issue When I execute top>a.txt and then open a window to execute cat a.txt, I find that the cat a.txt result is the result of multiple top templates, but I would not have this problem with other Linux systems In other Linux systems, the cat command only displays the results of the top command once I don't know why?