This is a ridiculous discussion, I suppose. You're accusing me of not bringing myself to attempt an answer to your question. You say mass is a number. It's something we invent to explain why we can weight things close to the earth's surface. Or why that sense of weight disappears when in free-fall. What acceleration is, and so on. Notice I use the word weight, not weigh. We use the first term for standard-mass objects, like a kg. But these are made of matter you say, not mass because mass is a number. So it dissolves to the semantic plane, what does mass mean or what does a number mean. Or what does red mean, or a solid ball of matter mean? What does rotation about a centre of mass mean. What could the centre of a number mean? I mention that a transparent glass bottle isn't in my head, like invented mass, it's "in" the bottle in exactly the same physical sense the glass is in the bottle. The qualities and quantities of the bottle are in the bottle, however or if ever, I perceive and interpret them.