Yes, going above 100% is possible. Zimmerman’s algorithm outputs a number that’s between 0% to 200%. To check the source data, you can go to the web interface -> side bar -> weather diagnostics, and see if any data (like temperature, humidity) might look wrong.
Also, please note that firmware 2.1.0 had a bug where if you’ve changed your OpenSprinkler’s HTTP port (to anything other than the default 80) it will fail to query the weather script. So if you are using firmware 2.1.0, and have changed the port number, the 114% you are seeing may be an old number that has not been updated.