The total number of feedbacks received since you joined is shown in brackets at the top of your feedback page, to the right of your username. This should continually rise as you receive new feedbacks.
The "Feedback ratings" for 1 month, 6 months and 12 months relate to the last 12 months only. These will change as older feedbacks fall outside the 12 month period, and newer feedbacks are added as you receive them.
Your percentage of positive feedbacks is calculated on the current 12 month period, so will likewise rise or fall monthly as the proportion of positive feedbacks is greater or smaller than in the previous period.