The actual Syns will depend on the flavour. Allow 1 Syn for every 20 calories, so if you have a 20g packet of lightly sea salted at 87 calories, then it's 4.5 Syns for the pack. However, a 30g pack of Sweet and Salty is 128 calories which is 6.5 Syns. The calories will be given on the packet.
(There is a Syns Value thread elsewhere on the forum - you would probably get a quicker response if you post similar enquiries there and it would save the moderators having to move posts).