Although appearing like calves, cows and cowherd boys, these were all Visnu. Actually they were visnu-tattva, not jiva-tattva. Brahma was surprised. The original cowherd boys and cows, he thought, are still where I put them last year. So who is it that is now keeping company with Krsna exactly as before? Where have they come from? Brahma was surprised that his mystic power had been neglected. Without touching the original cows and cowherd boys kept by Brahma, Krsna had created another assembly of calves and boys, who were all expansions of visnu-tattva. Thus Brahmas mystic power was superseded.