Direct Labour Build - Plastering/Slabbing

I am getting numerous quotes for plastering my 2000 sq ft 2-storey house. Some plasterers include 'slabbing' in the price. What exactly does this mean ? My walls are all block walls i.e. no stud partitions. Is it just attaching the plasterboard to battens/joists on the ceiling ?
If the total price of the plastering is say 10,000, what percentage would be slabbing ? Other plasterers dont include slabbing in the price so would I be better getting a carpenter to slab the ceilings ?

any advice appreciated...

If all the walls are block then presumably they mean a plasterboard ceiling. This is done pretty much as you discribe. They should provide a breakdown of the price between the slab work and the plaster work. Its impossible to give a % as i dont know what quantities of walls ceilings etc. Some tradesman tend to quote a lump sum for one off houses so it might be difficult to get a complete breakdown. On the issue of who slabs the ceilings i would recommend the plastering crew rather than seperate carpenters as if there is an issue with finish e.g. cracking then you have one point of contact rather than two trademen blaming each other for the cracks etc.