This records the total elapsed seconds covered by this bin's counter set for this E1 port. TT is the denominator needed to convert any of this port's other second-counters (ES, SES, UAS, AS) into a rate or percentage, since a raw count like 'UAS=30' is meaningless without knowing whether it happened in a 900-second bin or an 86,400-second one -- and this specific object covers the port's lifetime running total, with no periodic reset in this table -- a value that only ever grows. For example, over the port's entire lifetime with no periodic reset, this E1 port might show this counter at 86400 -- a concrete count the admin can trend against neighboring bins to judge whether the condition it reflects is worsening.