breakpoints perview

[peppeg85]

Hello, i'm trying to set the breakpoints perview number of slides, sorry, but i can't understand how it works.
if i set

     breakpoints: {
                    600: {
                        perView: 2
                    }, 
                   800: {
                        perView: 3
                    },
                    1500:{
                        perView: 4
                    }
                }

i expect to have 2 slides from 0 to 600 and from 600 to 800, 3 from 801 to 1500, and 4 after 1501.

now i have a random number of slides:
2 from 0 to 660
3 from 661 to 880
4 from 881 to 1650
3 after 1651

how can i fix this? are there any "internal" breakpoints?

thank you