The display I have is the one with the colon between 2nd and 3rd LED digit.
Using your code gives r i colon on colon off c c on the display.
As david said that is what the MSB does, 1 shows colon, 0 hides it, it is the difference between 0b10000000 and 0b0000000 on the 2nd digit in my case.
Now it is showing for example 1H:73 as of temp sensor 1 senses a temperature that is higher as the set max temp and adds H: to the display.