Can some one please explain to me the following... I'm just learning to crochet and this will be my first project...I am making this hat for my 7 mos old girl... I got lost on round 8th i don't know what to do next... Can someone help me go thru this project?? thanks lots

INSTRUCTIONS
Ch 4. Join with sl st in first ch to form a ring.
1st rnd: Ch 1. 6 sc in ring. Join with sl st in first sc.
2nd rnd: Ch 1. 2 sc in each sc around. Join with sl st in first sc. 12 sc.
3rd rnd: Ch 1. *2 sc in next sc. 1 sc in next sc. Rep from * around. Join with sl st in first sc. 18 sc.
4th rnd: Ch 1. *2 sc in next sc. 1 sc in each of next 2 sc. Rep from * around. Join with sl st in first sc. 24 sc.
5th rnd: Ch 1. *2 sc in next sc. 1 sc in each of next 3 sc. Rep from * around. Join with sl st in first sc. 30 sc.
6th rnd: Ch 1. *2 sc in next sc. 1 sc in each of next 4 sc. Rep from * around. Join with sl st in first sc. 36 sc.
7th rnd: Ch 1. *2 sc in next sc. 1 sc in each of next 5 sc. Rep from * around. Join with sl st in first sc. 42 sc.
*****This is where I got lost! I dont understand what does alt rnds mean?
8th and alt rnds: Ch 1. 1 sc in each sc around. Join with sl st in first sc.
9th rnd: Ch 1. *2 sc in next sc. 1 sc in each of next 6 sc. Rep from * around. Join with sl st in first sc. 48 sc.
11th rnd: Ch 1. *2 sc in next sc. 1 sc in each of next 7 sc. Rep from * around. Join with sl st in first sc. 54 sc.
12th rnd: As 8th rnd.
Cont in same manner, inc 6 sts on next and every following alt rnd to 72 (78-84-90) sc. Place marker at end of last rnd.

Rep 8th rnd until work from marked rnd measures 3 (3½-3¾-4) ins [7.5 (9-9.5-10) cm].

Ruffle: Next rnd: Ch 4 (counts as dc and ch 1). (1 dc. Ch 1. 1 dc) in same sp as sl st. *(Ch 1. 1 dc) 3 times in next sc. Rep from * around. Ch 1. Join with sl st to 3rd ch of ch 4. Fasten off.

Leslye