[{"storeNum":"71249","publicHealthUnit":"222","restrictionTracker":[{"dailyCapRunningTotal":30,"weeklyCapRUnningTotal":15},{"dailyCapRunningTotal":20,"weeklyCapRUnningTotal":10}]},{"storeNum":"71249","publicHealthUnit":"222","restrictionTracker":[{"dailyCapRunningTotal":30,"weeklyCapRUnningTotal":15},{"dailyCapRunningTotal":20,"weeklyCapRUnningTotal":10}]}]

db.collection.update({},/**filter criteria that matches all documents in collection*/{$set:{"restrictionTracker.$[].dailyCapRunningTotal":0/** `$[]` means all the elements of array will get updated*/}},{multi:true/** will update all the documents matching the filter criteria and not only the first document.*/})