'AT' your seat is defined as being within reach or touch of your chair.
'IN' your seat is defined as being seated in your chair, with the exception to allow a player to temporarily stand up.
A player must be 'IN' their seat by the time the last card is dealt, which completes the initial deal. A player NOT in their seat will have a 'dead hand.'
A player must remain 'IN' their seat until their action has been completed. A player LEAVING their seat before completing their action will be considered as intentionally folding out of turn and will receive a penalty. Dealers will be responsible to notify a Floor Person and/or the Tournament Director of any player with a live hand who intentionally leaves their seat prior to completing their action. Repeated infractions are subject to escalating penalties.
Players who have completed their action and are awaiting an opponent(s) action will not have to remain 'IN' their seat, but must remain 'AT' the table. A player must be 'AT' their seat by 'call' time, in order to turn their hand 'face up.'