What are scientist referring to when they speak about volume?

Whenever a scientist talks or speaks about volume, they mean "three-dimensional space". They often refer volume to as either a gas, liquid or a solid. The scientists calculate volume by, mass divided by density. Volume is often the calculation of what's inside a particular container. By knowing volume, it is easier to find out the concentration of the liquid, for example, that is in the container.   

You did not show us the image of the burger, but i shall try to answer as best i can.  when purchasing food, always consider the ingredients as well as the person who prepared it. consider if they were hygienic people or not, in case the burger was infected with bacteria. no mortal should place an infected burger into their mouth.