You should be able to hide it using the following CSS.
Code:
.cbUserListResultCount {
display: none;
}
You can output this CSS CBs built in CSS overrides usage shown below.
www.joomlapolis.com/blog/kyle/18711-template-css-overrides-made-easy
Is any add ons wich will show in e.g. module number of all user registered in CB?
Yup, the CB Online Module has several modes which can output various statistics like number of registers users. The module should already be installed and available for use in Extensions > Modules.