When Entering a cell in TAdvStringGrid

I am trying to understand how to set the grid and set the editor in a cell when entering it for example
cell contains 123 when you enter it by (Tab,Enter,Mouse Click) the editor highlights 123 and you type 4 the result of the cell is 4 not 1234.
Thanks
Steve

When all text is selected, it is normal that typing a new character will replace the selection.
To avoid that all is selected upon starting editing, set

grid.Navigation.EditSelectAll = false