It can be a little bit different if you use others values. Here's an example from zen_b1. Look at wait and random...
{
"classname" "func_timer"
"origin" "2707 3378 699"
"spawnflags" "1"
"target" "t5"
"wait" "0.7"
"random" "0.1"
}
{
"classname" "target_temp_entity"
"origin" "2666 3379 699"
"style" "45"
"targetname" "t5"
}