Why does my dog growl at me whenever I count?

I have a chihuahua, who's 1 1/2 years old, and whenever I count, he starts growling (It's not the playful kind either)! I figured out that he doesn't like me counting, whenever I was playing with him in my yard, and I was fixing to throw a ball. I started counting, and he started growling. I thought it was because he was growling at something else, at first. Then, I threw it and he growled again. So, I picked him up, and started sweet talking him, and he was very lovable, but when I started counting, he growls really nasty! I don't know why he growls like that when I count, he just does! Any help?