Use of THE after Verb-ing ?

We're going a bit beyond GMAT territory here, but I'll give it a shot. I'll also use a different example sentence to make it a bit clearer. I'm going to swap out 'more than 50' for the word 'many'. These words serve exactly the same purpose, but I think it's easier to 'hear' the difference when you use a shorter, more common word rather than an awkward-sounding phrase like 'more than 50'.

1. My daughter invited the many students in her kindergarten class to her birthday party.

2. My daughter invited many students in her kindergarten class to her birthday party.

In the first sentence, she invited all of the students in her class. In the second sentence, she invited many of them, but maybe not all of them. 'The' is a definite article; definite articles are used for a lot of different things in English, but one reason they're used is to express this particular distinction. 'The many students' means that you're talking about all of the students; 'many students' means you're talking about a lot of students, but it might not be all of the students in the room.

Similarly, 'the more than 50 plants' means you're talking about all of the plants; 'more than 50 plants' means you're talking about a particular number of plants, but it might not be all of them.