[Plugin: Simple Facebook Connect] og:description change size

You can use the sfc_excerpt_length filter to reduce the number of characters it tries to send. It’s set to 1000 (the max) because this increases the visibility of the post on Facebook.

Sorry for ask, and where I can find that function?
I’m looking the SFC plugin files and I do not find it.

It’s a filter, not a function. Put code like this into your own plugin or site to modify the value.

add_filter('sfc_excerpt_length','example_length');
function example_length($len) {
  return 500;
}