I don't think I agree with you
Why should the number of bytes allocate to the segment be 10485760 if both initial and next extents are 5242880.
When I multiplied 5242880 by 2, I got 104855760 which I think indicates that both the initial and next extents have been used.
So I am thinking that if initial and next extent have both been set to 5242880 and pct_increase is 0, then 5242880 will be allocated each time an extent has been used till the max extent of 450 will all being used.

CAn any one please intervene and help us out or probably correct us with this discussion?

NOTE: The initial and the next extent for the segment is 5242880, pct_increase is 0 and max extents is 450, So I do not agree with you saying the number of bytes allocated to the segment is 10485760

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