If R2=46, and HSYNC width is 14 then monitor hsync starts at 48 and lasts until 51.
On a CPC monitor, the HSYNC is rendered in "absolute black". It is darker than the black output by the Gate-Array.
The VSYNC is also modified before being sent to the monitor. It happens two lines* after the VSYNC from the CRTC and stay two lines (same cut rule if VSYNC is lower than 4). PAL (50Hz) does need two lines VSYNC_width, and 4us HSYNC_width.