Custom groups with rules included when dropped back onto the same or another form, will contain a special "Prefix" property. The property will automatically be given a unique value if you drop the group onto the same form 2 or more times. This ensures that the group controls have unique element name. You can view the impact the prefix has on the element names by viewing the form's schema or the control's property panel. Using the prefix property, you can write a separate rule to manipulate the 2nd or greater instance of the custom control. Refer to this documentation for the details.
The Max Size property is used to set the upper limit for each attachment uploaded using the Upload Control in your forms/flow. It is set to 10Mb in the