Your 3DFitBud step record can only be reset/cleared back to zero by holding down the RESET button on the back of your step counter for 3 seconds.
Make sure that the RESET button is not being pressed unintentionally, e.g. when sitting down with the step counter in your back pocket.

Please contact us if your step counter is resetting without any button contact.

Contact our Support Team by clicking 
here (or click on the 'New support ticket' option on the top-right of this page).
Or refer to the front page of your 3DFitBud Step Counter User Manual for other ways to contact us.
We stand by our product with excellent support.