The information on the datasheet is correct.
141.68 Watts (under load w/o HDD) / 452.68 Watts (under load with SAS HDD) for E310f
157.8 Watts (under load w/o HDD) / 468.8 Watts (under load with SAS HDD) for E310s

The E-Class unit ships with 2 x 400W power supplies  
For the 400W power supply, the AC power should be 597W (400/0.67).
.67 is assuming 67% efficiency

The power consumption number is calculated by taking the power consumption of the unit 141.68
and adding the power consumption of the SAS drives. In this case, we are using 300GB 15kRPM Seagate
SAS drives which based on their data and assuming 67% efficiency comes to 17.4W

So then we calculate as follows:

17.4 x 12 = 208.8 , 208.8/0.67 ~= 311.64 power consumption of 12 SAS drives

E310f - 141.68 311 ~= 452.68
E310s - 157.8 311 ~= 468.8

Both of these are under 597W, so the system can run on a single power supply.