This is the sequence of measuring lines. This P6 is the sixth measuring line and P7 is the seventh measuring line. Because it is suggested that a model needs so many two-dimensional lines, if you don't distinguish the lines on the overlapping surface in the end, you can't tell which constraint size it is.

Because UG is constrained, drawing will fail if it is over-constrained, so in the process of constraining dimensions, in case of over-constraint, you need to go back and delete the old dimensions.