The bull of the herd (meant for Vâyu) said to him: 'Satyakâma!' He replied: 'Sir!' The bull said: 'We have become a thousand, lead us to the house of the teacher;

In plain words: When the herd reached a thousand, the bull of the herd spoke to Satyakama by name. It told him the herd was now complete and asked him to lead them back to the teacher's house.