OBJECTIVE_LT meaning

[berylsheep-up]

GRIDS/execute/FlexiFixModelling.py

Line 104 in d92d55e

OBJECTIVE_LT.addTerms([1, 1, 2, 2, -1, -1],

Thanks for the excellent work!
In FlexiFixModelling.py L102~105, The OBJECTIVE_LT is T + L + 2B + 2R - W - H. I think the OBJECTIVE_GRIDCOUNT is to obtain the minimal number of grid-lines, but can not figure out what the OBJECTIVE_LT is. Can you help me?

Besides, the paper said that the equations (1) ~ (5) are to prevent the overlap of any pair of elements. But I do not understand how the equations can make sure it. I can not find more mathematical inference in the paper and supplement. Can you explain more about it? Thanks a lot!