Count number of values inside an array mongo PHP

I need to get the total number of array elements that are present inside the products array . So far i have tried using the $size=>$products approach but since technically there are two arrays only the value i get is 2 but i want to count the inner elements as well so that the desired result comes out to be 3.

I know i need to use $unwind but i cant figure out the approach.

{  
   _id:2,
   card_pay:3998,
   count:4598,
   orders:2,
   products:[  
      [  
         {  
            product_id:{  
               $oid:"5c63d418ae1db123d8048276"
            },
            amount:2499,
            quantity:1,
            status:1
         },
         {  
            product_id:{  
               $oid:"5c46f7f329067970211471a0"
            },
            amount:200,
            quantity:2,
            status:1
         }
      ],
      [  
         {  
            product_id:{  
               $oid:"5c63d3afae1db123d8048273"
            },
            amount:1499,
            quantity:1,
            status:1
         }
      ]
   ]
}