Our size chart are all flat measurement. That is measure when the item is laying flat on a flat surface.
The best way to choose the size is by measuring a pair of leggings or top that fits well and compare with our size chart.
All measurements in cm
The weight and height chart recommendation is for reference only. You must factor in muscle density also.
As for the recommendation below the description, it is from the experience of our testers. When we say choose one size up, it means when they usually wear a M they rather choose an L for that specific style.