It's been 2 years since I bought them. I do recall the salesman used a computer program in which he entered the dimensions of my shop. He allowed a foot for the chains attaching the lamps to the ceiling and a work surface of 40" for bench work. IIRC - he came up with 70FC -- that is a very fuzzy number.
Found this on-line. Hope it helps:
Specifications
Input Line Voltage 120-277V
Input Line Frequency (Hz) 50/60HZ
Lumens / Wattage A Package –2 ft: 2600 (20W), 4 ft: 4200 (32W), 8 ft: 8500 (65W)
B Package –4 ft: 2300 (18W), 8 ft: 4900 (38W)
Lumens per Watt (LPW) >130
Color Temperature (CCT) 3500K, 4000K & 5000K
Dimming 0-10V (standard)
Controls Occupancy sensor w/ daylight
harvesting (optional)
Rated Life >50,000 hours
Operating Temperature --20°C to 50°C
CRI 80+
Power Factor >0.9
THD <20%