Limit number of text outputted using Meteor blaze

I have an app that accepts the 1000 minimum character as input, when i want to display it on the screen only about 400 characters should be dislayed but i seem not to have found away of how to do this. This helper class returns an object, so via this all the variables can be accessed

Template helper

Template.SchoolDashboardLayout.helpers({
    selected: function () {
    return Session.equals('selectedSchool', this.__originalId) ? 'selected' : '';
}
})

This is the frontend using blaze which returns all the 1000 characters but I want to limit the display to only 400 characters, how do i do this? Thank you very much.

<span> {{sellschoolvar}} </span>