Repeated foot steps sent by garmin API

We have taken steps count from garmin API to our app, 

we are getting the necessary data (foot steps) but we have got a issue of repeated step count.

Like, we have 40 steps today, and we have sync at 6:00 AM , it gives accurate data . but again after  20 steps at 6:30 AM we sync again then the previous sync data  will also add up (40 + 20 =60 steps and the previous 40 )= 100 final steps will be 100.

but in actual it must be 40+20=60   

we haven't store any steps in our database , whatever Garmin API send us we have used . Garmin support reply us that GArmin API has send only single data , but we are getting multiple data.