They are changed position, the top one is down, the bottom one must be loaded with water and the top one empty, when the bottom one weighs, (it should not be regulated at the bottom, but 1/3 or 1/2 of the tank ), the engine starts, and when the water reaches the top, (at 1/8 or 1/10 dfel tank), it floats and relieves the load, then stops the engine. luck
I do not remember but I always put them together, whatever the brand, I never had any problem except the last two that I placed (in the same circuit) that is seen to have played a bad game and in a matter of a couple of months they called me to change first one and then the other, both had broken the microswitch, replace them with submersibles and never again
If you use logic ... The buoy below has to go with the hole up so that it stays full of water and makes weight
And the buoy above has to go with the hollow down so that it lifts the weight since when covering the water inside the buoy an air chamber is formed capable of lifting the buoy below and inverting the switch and also preventing it fill with water since this happens the system does not work