The number indicates the minute it restocks. For example for the shops that restock at 0/5 every time the minutes ends in 0 or 5 is when it will restock - as in 1:00, 1:05, 1:10, 1:15, 1:20, 1:25 etc. It is the same for the rest 1/6 would be 1:01, 1:06 and so forth.

Restock Times:

0/5
Pots of Paint
Musical Instruments
DVDs
Tools
Contact Lenses
Batteries
Computers
Vegetables
Flowers
Frozen Foods
Male Clothing
Cleaning Product
Sunglasses
1/6
Glowing Eggs
School Supplies
Mini Pets
Costumes
Appliances
Female Shoes
Seeds
Weapons
Chocolate
Balloons
Sushi
Pearls
Minipet Food
2/7
Gourmet Meat
Candy
Soft Drinks
Armour
Wallpaper
Wigs
Male Shoes
Illegal Concocotions
Bakery
Halloween Treats
Pizza
Giant Vegetables
3/8
Giant Flowers
Ice Cream
Furniture
Stars
Voodoo Dolls
Potions
Books
Fruits
Fast Food
Car Parts
Hair Dye
Canned Food
4/9
CDs
Toys
Stamps
Flooring
Female Clothing
Cooking Ingredients
Medicine
Giant Fruits
Trading Cards
Magic
Lipstick
Charms