Real consumption of SMD5050 Led Strips
This is the difference between max current (20ma per channel per diode) and actual current. If you look at the resistor values on your strip you can calculate the actual current the diodes will receive. In this case it is obviously a lot less than the nominal 20ma max for 5050 diodes.

And yes, if you have strips that drive each diode at 10ma instead of 20ma, you can have twice as many diodes per power supply.