You can actually avoid using trunctation. Consider that if @t is the sql agent time, @t % 100 will be seconds, @t % 10000 - @t % 100 will be minutes * 100, and @t - @t % 10000 will be hours * 10000. So, the subsequent division by 100 or 10000 is already an integer value.

DECLARE @t int = 1234556; --4546 --5; --56; --1234556;

SELECT

@t AS AgentDuration,

(@t - @t % 10000) /10000 AS hours,

(@t % 10000 - @t % 100) /100 AS minutes,

@t % 100 AS SECONDS,

((@t - @t % 10000) /10000) * 60 * 60

+ ((@t % 10000 - @t % 100) /100) * 60

+ @t % 100 AS totalseconds

Added bonus: it'll work for negative values too. Not that output will mean anything (GIGO!)