Roundup Pro Max comes in a 1.67 gallon jug.
Since Roundup Pro Max is a non selective herbicide that kills anything it is applied to, it would not be recommended to tank mix with fertilizers.
Roundup Pro Max would not be applied over areas that have been seeded. You would need to wait at least 2 weeks after applying before seeding the area. After seeding you would need to handle pull any weeds until the plants are established and then can spot treat with the product taking care to avoid spraying them directly or allowing drift to contact them.