When the table is truncated the table is reseeded with values back to 1 again.
Technically, the table is set back so that the next row inserted gets the initial seed/starting value, which is usually 1 but could be something else.
SQL DBA,SQL Server MVP(07, 08, 09) Prosecutor James Blackburn, in closing argument in the Fatal Vision murders trial:
If in the future, you should cry a tear, cry one for them [the murder victims]. If in the future, you should say a prayer, say one for them. And if in the future, you should light a candle, light one for them.