In the ship discriptions theres an entry called Accel: max acceleration. I dont see any rules that govern this. Example below, what does this mean as the ship already has a Speed stat.

Accel: 4.3 gravities max sustainable acceleration

I can't point to the rules, but for short-distance chases Acceleration is more important then maximum speed.

A ship with a high acceleration may catch up with another that has a higher top-speed, before the other ship has managed to achieve said high speed.

1 Gravity is 9,8 m/s^2, meaning that each second the speed is increased by almost 10m/s (about 35,3 km/h)

Cpt. Harkonnen said:

It means nothing. It's just fluff.

It gives you an indication of how quickly your ship can reach her maximum speed, as well what kind of gravitic pull she can escape easily.

Indeed there may not be mechanics for gravities of planets and ship acceleration but if your bulk-transport ship has less than 1g of Acceleration it isn't going to be able to leave orbit of a Terra-style planet EVER!

Kasatka said:

1g is the force of acceleration at sea surface level here on earth. It is significantly less as you move away from earths centre of mass, and when you're in orbit, you're effectively in free-fall. So even with a minimal thrust, you will break orbit easily.

Now, if you talk about a rocket that was to take off from the surface, you're quite right

It's fluff, got, thanks!

It's also relatively inconsistent with the stated masses of the ships. FFG really should have hired a physicist/mathematician/statistician to come up with better mass and accel numbers for their ships, because the densities and crew per volume , and volume per space measures vary wildly.