Revolution Slider – Limit The Excerpt To

Hi,

I would like to show excerpt of my blog posts. There is “Limit The Excerpt To” option, which I supose should limit number of characters from post in slider. I tried different values, but they have no effect (see atached screenshots).
I have Revolution Slider 4.5.9 and HE theme 1.5.
How can I limit excerpt (post content) length to for example 50 characters?

Thank you