In my experience with sepia toner.....
The Bleach time dictates the tone. You need to tone for 1 minute or more, or at least until the print stops changing.
With Ilfords MGFB paper, the tone seems to be less sepia, more redish.
If you limit your bleach time you will affect the high lights and midtones more... and you will leave the shadows/blacks alone.
I hope this helps.