When a Yaa Saakin (يْ) appears before a Raa Mouquf and the letter preceding the Yaa Saakin has a Kasrah (ِ), then the Raa (ر) will be recited with an empty mouth.
When a letter other than a Yaa Saakin (يْ) appears before a Raa Mauquf, and the letter has a Sukoon ( ْ) on it and the letter preceding it has either a Fathah (َ) or Dammah (ُ) on it, then the Raa (ر) will be recited with a full mouth.
Aswaatul Qurraa is intended to enhance the learning process for aspirant Huffaadh and at the same time is meant as a tribute to those who love reciting and listening to the Quran