Bruce Almighty, the key on page 203 refers to the drawing on that page. In the other drawings to which you refer, the boxes describe the construction, distinguishing between notional and full 30 minutes.
Let me see if can clarify; when you used to change the oil of the Dennis under the watchful eye of the sub-officer, there was a symbol in the schematic of the engine compartment that said water pump. But BruceAlmighty (aka BA) it was talking about the said component for cooling of the engine (which you constantly overran in your haste to return to your card school on Wed evenings, or your snooker for most day shifts or your bed if the fire was after 1700). On a further page of the manual, there was a different water pump, for which the above symbol did not apply, that you used to drown the building and its environs with water to deal with waste skip fires.
Hope this helps. I remain your humble servant.
PS we will be running training courses on the guide for which you, personally, could obtain a discounted rate.
PPS Tam, I never assumed you knew half as much as I.
