For volume autosize documentation Click Here
You can configure the Minimum and Maximum size for autogrow (as well as threshold)
but you will not be able to configure the size each time it increase.
here is my reason (or understanding)
Currently you have a 100 GB volume..
And you set.. the autogro options as follows..
Mimimum size is 100GB
maximum size is 50TB
Yes, -maximum-size can be set upto the platform-dependent maximum FlexVol volume size.
if ontap let you configure the increment size and you set them as 50G.. while the volume size is 100G or 200G it will make sense.. to add 50G
but it won't make sense to add 50G to once the volume is 25TB or 30TB...
in order to avoid that, (resizing the volume every minute) ontap calculate the size based on the tresholds & policy you set, and add that each time if necessary.
hope this help..