I think it's already been covered here, but for clarity's sake here's my two cents' worth,...
Diffusion light sources (aka dichroic colour heads) are typically lower in contrast than condenser heads; therefore (B&W) film is usually developed slightly longer to correct for this. It's all relative.
In densitometric terms, it's as follows:
Zone I exposure: 0.10 above fb+f (up to .20 a la Mr. Hutchings)
Zone VIII exposure: 1.25 to 1.35 (net) above fb+f for a diffusion enlarger
Zone VIII exposure: 1.15 to 1.25 (net) above fb+f for a condenser enlarger
For the sake of reference, your Zone V exposure should be as follows:
Zone V exposure: 0.65 to 0.75 (net) above fb+f for a diffusion enlarger
Zone V exposure: 0.60 to 0.70 (net) above fb+f for a condenser enlarger