Centered scale with value

Hi I have a question about the scale tool.

I need to scale my object using the ctrl key to scale it mantaining the center.
I have to scale it with a precise value inserting it with keyboard and not using the mouse positioning.
How to do it?
If I’m holding the CTRL key, i can’t insert value manually and if I leave the CTRL key the object will not be scaled by the center.
Is there a way to do it?

Thank you!

Ok, maybe I found it bymysef.
I have to start scaling with the ctrl key pressed, then leave the release the mouse button keeping the ctrl key pressed, then release CTRL and insert the value.
Is this correct?

Start the move with Ctrl pressed then just let go of both the mouse and ctrl and type what you need and hit enter.

An important thing i notice, is that the scaling action can be done in two ways:

  1. pressing once the left mouse button and then move the mouse in the desired direction
  2. keeping pressing the left mouse button.

the #1 way don’t work if you want to keep the scaling centered

Yes if you use the click and release method you need to click and release again to end the action then type your specifics.