When you don't have too many votes cast, it doesn't take much to cause a big swing. There is a section in the code where it doesn't actually calculate the attitude until after 3 votes are cast, but perhaps that should be increased.
If you want to see exactly how it is done, here is the code reference. Basically, it is just a number between -1 and 1 (-100% to 100%) based on the votes you have made. It can be different on different instances depending on what has federated to where. For example, on instances with downvotes disabled, everybody has a 100% attitude!
wjs018 @ wjs018 @piefed.wjs018.xyz Posts 0Comments 23Joined 4 wk. ago
Specifically, from looking at the code, it counts the most recent 50 votes on posts and the most recent 50 votes on comments for the calculation.