You can have more than one thing for snacks. Many of us have a "mini meal" at snacks, for instance, I might have dried apricots & a LF cheese stick (like I did today) or baby carrots and a LF cheese stick. You could have yogurt and a cheese stick if you wanted. The yogurt is a milk & the cheese stick is a protein. It's not really a rule, but when I have a "mini meal" for snack I typically try to eat foods in different groups.
You can have up to 2 cups of milk/ yogurt daily, like Stacy said. You can eat/drink it all in one sitting, 2, or however many you want. In other words you can have any amount up to 2 cups of yogurt. Keep in mind though, that in phase 1, you can have only low-fat or non-fat PLAIN yogurt. You can add vanilla & Splenda or other approved flavorings to it though.
The quantity of nuts is different depending on what kind of nuts you are eating, and there is a IMIT of ONE SERVING/ DAY.
almonds: 15
Brazil nuts: 4
Cashews:15
chestnuts: 6
Filberts: 25
Edamame: 1/4 cup
flax seed: 3 TBSP
hazelnuts: 25
macadamias: 8
natural peanut butter or other natural nut butters: 2 TBSP
peanuts, dry roasted or boiled: 20 small
pecans: 15
pine nuts: 1 oz
pistachios: 30...my favorite nut to snack on because you get so many!
pumpkin seeds: 3 TBSP
sesame seeds: 3 TBSP
soy nuts: 1/4 cup
sunflower seeds: 3 TBSP
walnuts: 15