broken heart line point toward mercury

[happi]

when it says mercury qualities causes the break, what does it exactly mean.
what exactly are mercury qualities.

the line am studying is broken under the mount of Saturn and inch long branch  goes toward a mercury finger, affection or health defect, am not sure. however person said he is going through bad depression due to worry about his affection and have extra worries which make him feel that nothing is going well. person is also suffering to head related problems.

could some one with more knowledge please explain this.

thank you