Setting Minimum Quantities, Maximum Quantities, and Increment on Instabuy
InstaBuy supports adding minimum quantities per product, and also maximum quantities custom increments
Do be aware though that customers can change these in the cart, so they're for convenience rather than security.
You can assign these values by adding tags to your products in the following format:
So to have a product that the customer must add at least 12 to the cart, and then can order in multiples of 6 (but no more than 72 each time), add these three tags:
Make sure you don't add a space inside the tag. You can of course mix and match just the tags you need.
You can add tags to products in bulk in your Shopify admin 'Products' section.