How is THIS possible?? - National Grid related

I had someone come read my meter on July 23. They put in that the actual reading was 5992. I just received another bill for another reading August 15th it says the actual reading is 5992. Now yes, we were away for 2 weeks between 7/23-8/15 but does that mean we used 0 gas, um no. My stove and water are both heated by gas