The phrase "small glass" refers to a drinking container that is smaller in size. It means that the glass is not as big as other glasses and can hold less liquid.
I also can the peaches for holiday gift giving in small glass jars. (recipegirl.com)
I'll be making some more of this, and doing what the teacher did — seal them in small glass jars to enjoy all summer long. (browneyedbaker.com)
Place chocolate chips and oil in small glass bowl; microwave on medium - high until chocolate is melted, stopping occasionally to stir, about 1 1/2 minutes. (epicurious.com)