How can i find out how many more bottles of Nuka-Cola Quantum I need to donate?

I'm working on the Nuka-Cola Challenge, but as the bottles are few and far between I don't know how to keep track of how many I've already donated, or how many more I need to find.

When I donate any, Sierra says 'you've found more than 10...' or words to that effect, but I can't find any stats telling me how many more I need.

Do I just keep finding them and delivering, hoping I hit the magic number, or is there a more precise way to know?

Unfortunately, I don't believe there is any kind of counter that is available to the player, apart from this one speech option:

• When exactly 30 Nuka-Cola Quantums are in the inventory, a speech option of "I HAVE THE LAST OF THE QUANTUM!", will appear.

  • This removes 30 Nuka-Cola Quantums from the inventory and completes the quest, but be careful towards the end of giving Sierra your Quantums, as she may take more than 30 if given the opportunity. She will say that the Lone Wanderer has given her "over 25" Quantums---so if she has actually been given 29, but there is more than 1 in the inventory, she will take all of them.

Source

Note: This does need clarification as to whether or not this option appears if you have been donating them one at a time, the line "if she has actually been given 29, but there is more than 1 in the inventory, she will take all of them" suggests that this might be the case.

So to clarify; the only indication or counter of how many Nuka-Cola you have been donating is

• if you have up to, or over the total amount of Nuka-Cola that has already been donated, and have the remainder in your inventory
• or you have all of the Nuka-Cola in your inventory (all 30)

and you will be given the final speech option.