Why is pid changed in different terminal session?

I use WSL2 and was trying to use gdb to debug a c code following this gdb cheatsheet. In summary it shows a way to call a python code solve.py that calls a c code, and displays the pid of itself. And in another terminal session, I run gdb to communicate with the solve.py process by specifying the pid of solve.py. However I realized I was failing to communicate with solve.py because the process pid was wrong. I ran ps and found out the solve.py was slightly different with what I saw in the first terminal. Can anyone explain why? Below is a demonstration. (env) junha@DESKTOP-3B9ANKQ:~/cs2107$ python3 solve.py [+] Starting local process './test': pid 627 [*] Paused (press any to continue) then I am supposed to run gdb -p 627 as given in the cheatsheet. But it doesn't work, and when I use ps a, I see that the actually pid is 624 not 627. junha@DESKTOP-3B9ANKQ:~$ ps a PID TTY STAT TIME COMMAND 226 hvc0 Ss+ 0:00 /sbin/agetty -o -p -- \u --noclear --keep-baud - 115200,38400,9600 vt220 231 tty1 Ss+ 0:00 /sbin/agetty -o -p -- \u --noclear - linux 388 pts/0 Ss 0:00 -bash 389 pts/1 Ss 0:00 /bin/login -f 508 pts/1 S+ 0:00 -bash 573 pts/2 Ss 0:00 -bash 624 pts/0 S+ 0:00 python3 solve.py 627 pts/3 Ss+ 0:00 ./test 629 pts/2 R+ 0:00 ps a and below works: gdb -p 624