What is Make it Global block setting mean? and How to add more slide

I have 2 question.

1. What is Make it Global in the block setting mean? What is suppose to do. I try few time with same or different block but not see what it did to the blocks.

2. How I can add more than 2 slides? I have transform block into slide then it appear 2 slides as default. Do we able to add more than 2? Although slide make the page builder really slow but as I write review about it I would like to know.

I am writing review about Brizy so I want to make thing clear.