The amplifier is turned down, narrowing the SEM scan. The V then occupies a larger fraction of the electron beam's path (that is, the electron beam reaches the V sooner as it scans in from the edges of its pattern).
The synchronized pattern on the CRT (fixed at full screen size) then displays a magnified image of the V.
The SEM scan can then be further reduced to smaller and smaller areas. As long as the electron beam is narrow enough, this will produce ever increasing magnification of the scanned area.
