Proportional Proposition meaning?

shbvans1126

Hi, folks
I came to cross PT 70 sec1 Q11, and started to wonder what proportional propositions imply.
Let’s say “The more A, the more B” is given as a Premise, not Conclusion

Does this mean that the Only contributing factor to B is the A, regardless of any other factors?

Since it literally means the more A, the more B, if A goes up, then B should go up, right?
Then as long as A is more, then other factors doesn’t matter?
OR is the proposition imply that “if all other factors are equal”? So even if A rises, if the other factors are not equal and offset the proportional relationship between A and B?