Note that an average body weight for an average woman is around 120lbs, Egwene is able to lift 3 women (while splitting her flows 4 ways) 10-12 Spans in the air (so about 360ish lbs, 3-4 stories high). We also know that this was not easy, but clearly not her limit as it wasn't difficult either. Given that Siuan at full strength could lift about 250lbs and Egwene is just a little less than 2x stronger than Siuan was, Egwene may be able to lift around 430-450lbs.

WH
Blue Carp Street

"I saw them," Rand said. "They're inside now. Nynaeve, can you lift Lan and me to that rooftop from the alley behind the building?"

Nynaeve frowned at Zeram's building, rubbing the belt around her waist with one hand. "One at a time, I could," she said finally. "But it would use more than half what the Well holds. I wouldn't be able to lift you down again."

2 men of 6'6" each with all that equipment would weigh in around 250lbs (that's assuming they are both muscular and have some equipment since an average BMI for a man this size would make him more like 200lbs). Nynaeve's Well holds enough Saidar to lift them both the 3 stories to the top of the building, but she cannot do it at the same time. So without splitting her flows Nynaeve cannot lift 500-odd pounds 3 stories.

and yes it's 3 stories she needs to lift them