Your just not able to understand simple matters. No, he was not referring to the numbers required in his first teshuvah, since he never mentioned numbers there. Your being silly for hanging onto words that are irrelevant to the conversation. Lets try explain Rav Moshe’s shita regarding shishim ribo again:
Like most poskim, Rav Moshe originally maintained (Igros Moshe, O.C. 1:109) that the criterion of shishim ribo was dependent on the street having shishim ribo traversing it. However, later (ibid., 1:139:5) he formulated his chiddush in which shishim ribo when applied to a city was not dependent on a street but over a 12 mil by 12 mil area. Rav Moshe added that the criterion of shishim ribo ovrim bo would require a sizable population living and commuting into the 12 mil by 12 mil area so that it could physically satisfy the condition of 600,000 people collectively traversing its streets. However, at this time Rav Moshe did not quantifying how many people would be required to live in this 12 mil by 12 mil area.
In the first teshuvah quantifying how many people would be required to live in this 12 mil by 12 mil area, Rav Moshe stated (ibid., 4:87) that since in the past eruvin had been erected in cities with populations exceeding shishim ribo, one could not classify a city as a reshus harabbim solely on the basis of the existence of a population of 600,000. He then added that although the actual number of inhabitants could possibly vary according to the city, in Brooklyn it would most likely require four to five times shishim ribo. In the final two teshuvos which followed regarding Brooklyn we see that Rav Moshe codified his chiddush that the requirement is, “just about three million people,” (ibid., 5:28:5) or, “at least five times shishim ribo,” (ibid., 5:29) which could amount to even more than 3 million people. Consequently, in the Chicago eruv pamphlet (West Rogers Park Eruv, 1993 p. 23) it is stated that Rav Dovid Feinstein shlita was in agreement that according to his father’s shitah there must be a minimum of 3 million people in order for the city to be defined as a reshus harabbim.