What does "C" in front of the premium mean (TWS)?

[mutluit]

Hi,
forgive for this maybe silly IB TWS related question but I couldn't find what it means, and such things really bug me:
In Options Trader there is with _some_ premiums the letter "C" in front of the premium, like C2.68.
Example: MSFT Oct 34 and 35 Puts
What does this mean?
Thx

 

[swingtrader123]

It means that was the closing price for the option. It also means that particular option has not traded yet.