Lumen is light output. That term is used instead of the old watts terminology as it is more accurate a representation of the light from the bulb.
Foot candles is the measurement of what yore lighting. So 277 foot candles on the field, is comparable to having 277 candles burning per square foot.
I’m aware of what a lumen is. The other guy apparently doesn’t have a clue. If an incandescent bulb and an LED bulb each put out 500 lumens, they are equal in terms of light output. Other guy is trying to declare that the type of bulb matters in this measurement. It’s like saying a mile is a different length measurement for walking than it is in a car. It’s ridiculous.