Use floatround.
Code:
public Left_20(id) {
set_hudmessage(255, 255, 255, -1.0, 0.26, 1, 2.0, iSeconds, 0.1, 0.1, 1);
if(is_user_alive(id)){
switch(cs_get_user_team(id)){
case CS_TEAM_T: show_hudmessage( id, "Seekers Are Frozen So You Can Hide!");
case CS_TEAM_CT: show_hudmessage( id, "Hiders Get %d Secs To Hide!", floatround(iSeconds));
}
}
}