Mild, trivial, are adjectives for the degree of valve leakage, and it is not considered medically significant. The condition often does not progress nor cause symptoms. Borderline probably means it is not clearly observed whether or not there is leakage...it is apparent it is not an medical issue.
The pulmonary artery pressure represents the amount of resistance the right ventricle pumps against. More resistance the higher the higer the pressure. Resistance can be narrowing of the pulmonary vessel, thrombosis (blood clots). High PH (systolic) can be associated with age, body size, gender, etc.wall thickness, and ejection fraction. The 40 mm Hg is the upper limit of the reference range for normal.
Hope this helps, and if you have any followup questions you are welcome to respond. Thanks for the question, take care.