This is usually more confusing in Bass anglers. Ppl buying line base off advertised lb test that claim one brand better than others and such. And when there are no standard some manufacturers use thicker line in similar lb test compared to others then the advertises of better line abrasions and strength.
I normally buy line base on diameter and characteristics not just lb test for different techniques. If in doubt I’ll base off JDM line which usually more standardized across the board.
I used to measure each line with digital calipers, the most favorite among bass anglers, yo-Zuri hybrid 6lb test has the same diameter with 7-8 lb other copolymer/mono compare to 9-10lb JDM fluorocarbon.