The mystery is solved. I have corresponded with Charlie Oppenheim in the Visa Office. He confirmed that the 27% limit does apply. He explained that during this fiscal year, the CIS consumed an unusually large number of Indian EB2 visas, thus making the category unavailable despite a retrogression in the cuoff date which was intended to hold number use within the limit.
He said that based on his discussions with the CIS, he was informed that the CIS did not feel that the current amount of pending Indian first preference demand would be insufficient to use all available numbers under the limit. Therefore, he allowed some of those numbers to fall down into Indian second preference.
So, the Indian second preference numbers used to establish a cutoff date for April are coming from left over Indian first preference, not worldwide numbers.
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