What a series is truncated against: the observation’s own ceiling, the amplitude a
dropped tail provably stays within, and the floor a tail no bound sums falls under.
Each direct sum a row takes over this form’s lines, as its rounding bound and the factor it
is read under: none on a line row, the group’s own on a windowed one.
FORMAT 6.2 truncates a series once, at collapse: every term the ceiling and the precision
leave becomes an ordinary atom before the first sample is read.