The symbol that is displayed on the monitor is flashing underline to indicate or suggest that the next one is in the position where it may be underlined or in a box that says you're a location somewhere on the screen.
The symbol displayed on the monitor is underlined or flashing to indicate that. Where is the next position It can be a symbol underlined. Or box that says you are not on the screen.
The symbol displayed on the monitor is underlined flashing to show or indicate the next position which may be symbols are underlined. Or a box, which said you were in position on the screen!