Hi raheelqaiser2,

This is an old and known bug.

Most VNC systems implements their authentication using DES encryption (https://en.wikipedia.org/wiki/Data_Encryption_Standard).
You can read more about the details on the Wikipedia link, but in short, DES limits key sizes to 8 bytes (characters). Passwords shorter than 8 are padded with zeroes.

Some implementations allows passwords to be longer than 8 (RealVNC allows 255 for example). But then, if you connect to a server that is using the standard authentication implementation, your password will just be silently be trimmed to 8 characters, ignoring anything beyond that.

Hope this helps.