Hola Linda

You can use the future to simply state when things will definitely happen:

Or you can also use it indicating that something will probably happen at a certain moment in the future. When we use it this way, there is normally something else in the sentence that creates this uncertainty, or sometimes that uncertainty goes simply with your facial expression (of doubt), so there will be some kind of indicator. 

In this specific example we are creating that sense of "might" by saying first "Estoy muy ocupada... así que..." This makes the listener think that that may be a "might" arrive at 12. 

Saludos

Inma

Hola Denise

We've added a bit more clarification to the lesson so it's clearer when we use the future tense with this purpose and added some hints to the test-questions. I hope this clarifies it. 

Using the Spanish simple future to express probabilities or predictions in the future (El Futuro Simple)

Gracias y saludos

Inma