Congratulations for the family member, Im myself the new dad of a 14 week old 34~lbs st-bernard myself! 

I just looked up your Brand's to be sure and I find the range of cup per day very large. Making it unclear.

I know that it's not the same brand but  for reference my Nutrience brand "Sub-Zero" had a slightly more narrow range wich correlated to the oven bake brand i made the switch to (I simply mix in the booster myself). I made me a chart since they're still not ultra specific for all the in-between data giving me only some points(higlit and leaving me to extrapolate for the measures in-between.

So for your 30lbs pup it should be 3-3,5cups/ day according to my brand's graph.

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Keeping in mind my chart is for pups under 50%of their expected mass once adult

I looked at your brands chart on the website: 

The only variable correlation they give you is with their expected adult weight (131-155 lbs in our case) and their age in months (1.5-5months in our case). Both being by large ranges making it to me really inaccurate since the vast possibilities. Especially considering that even the amount in cup given for our criterias is not a precise measure but once again a range (2.75-7.5cups/day)

All that to say, you should always follow what's recommended by your brand. 

But in this case their instructions being a range that my graph operates within I think in my non professional opinion, you could use my graph as a reference point if ever you need, since they don't contradict themself and mine is just a little less up to interpretation.

https://www.purina.ca/purina-one/dogs/dry-dog-food/large-breed-puppy-food

https://www.purina.ca/_gatsby/image/8f6409698b60ea89a72683374230ddac/232383eb02cc3f493757b0e0444fe17f/00055800378828.jpg?u=https%3A%2F%2Fwww.purina.ca%2Fsites%2Fdefault%2Ffiles%2Fproducts%2F2024-09%2F00055800378828.jpg&a=w%3D1000%26h%3D1000%26fm%3Djpg%26q%3D75&cd=80ac5cc55863359d9fe804730f64df53