INA138 Reference Design Question

This is in regards to the TI reference design titled "High Voltage 12 V – 400 V DC Current Sense Reference Design" (TIDA-00332). I recreated the design with the only difference being that instead of 400 V, 380 V is used. Everything works as described but I noticed that a noticeable amount of heat is being generated by the INA138 IC. The temperature stabilizes around 65-70 C. This is below the maximum thermal rating but I was still curious as to if this is what to expect and the cause for the heat generation. I tried looking at the data sheet but did not see much in regards to that.