According to the problem, Abby wrote a sentence about multiples of 5. Remember that a multiple is a number that can be divide by 5, in other words, we can express a multiple of 5 every number with form 5k.
Additionally, Abby noticed that multiples more than 5 and one less than five are also valid.
So, Abby's statement is conjecture. She has not shown that her statement is true for all values of n. The pattern she noticed for the first 20 values of n may not extend to all other values of n.
It's important to say that Abby made a conjecture, which means she didn't prove in a general case for all natural numbers.