score:4
The information given on your tickets is accurate. If the ticket says 30, it's 30. If it says 45, it's 45. Any weight exceeding that will have to be paid for or removed.
Practically, what this means for you is that you can carry more on the way back than you can on the way out. I guess you will be able to bring a lot of souvenirs if you want to.
Adding @Willeke's comment to the answer: Most airports have an upper limit of 32 kg max per item, I do not remember any that exceed that. It is in EU law that workers do not have to lift more than that even with two people working. 45 kg has to be in two items of luggage.