The volume markers on the S-bottle are not calibrated. The safe margin for deviation on any baby bottle is maximum 5%, regardless of the age of your baby and the volume of food you are feeding.
Example: If you are feeding 50ml of food, the volume in the S-bottle can be a maximum of 2.5ml under of over this. If the deviation is more than 2.5ml on a 50ml feed, as in this example, we will honour the warranty on the bottle.
The volume markers on the cap of the S-bottle are calibrated. The caps to the bottles all feature volume markers. If you need to measure food very precisely, you can use the cap to the S-bottle for this.