The 2 diagrams mean the exact same thing but the first one is simple and easier to understand and the second one is a compact version of the first one.
t is not bad if Muslims marry Hindu or any other non-Muslim girl whether Christian, Jew or Sikh. But I am referring to Hindu girls as they are in majority in India.
In short this is what the above diagram means:
A Hindu girl Marries a Muslim then they have kids who are also Muslim then again the cycle repeats.When those Muslim kids grow up one of them again marries a Hindu girl and they again have kids. Then again the same cycle repeats, the cycle should keep on repeating and this should go on from one generation to the next generation.
Secondly, Muslim means one who submits to Allah and one of the duty of a Muslim should be to enlighten others, propagate true religion ie; Islam and bring people to the right path. So if a Muslim marries lets say a Hindu girl then it also means he is bringing that girl to the right path of Islam.
Thirdly, if a girl from other faith marries a Muslim then it also means she has got liberated from a false religion which she was previously belonged to.
In India it is happening and is good for the country as it will also eradicate caste system. Hindu religion has caste system and most of the Hindu families want their girls to marry in the same caste and they don't want their them to get married in lower caste or even different cast. But Muslim families are not like this they happily accept Hindu girl after she has accepted the truth and willingly converted to Islam.
In modern India Hindu girls are working every were in both private and public sector along with men. Muslims are also getting educated and working every where so it is easier for them so socialize with Hindu girls. Where as Muslims girls are modest and dignified they are hardly seen working outside along with men.
This is one of the reasons why conversion before marriage is important because usually Hindu and other Non Muslims girls can be indecent especially Hindu girls because its in their culture to expose which has been emphasized by us in this post (http://indianmuslimpost.blogspot.in/2013/01/why-hindu-girls-show-their-body.html), they don't dress modestly but after accepting the truth ie; Islam they start living a modest and respectful life as a Muslim women. So its good if a Muslim marries them and shows them the right path.