See other notes that are tagged "en- and em-dashes" for explanation. This actually isn't such a big deal IMO, esp. if it's consistent throughout the entire publication. But if you wanted to know about it, it's there. Let's face it: Most folks reading this probably won't care a bit (or even know about) the distinction or rules. So, you can probably ignore anything that's labeled as such (tag: en- and em-dashes).

OK, two things: en-dashes and em-dashes, and spacing with regard to each.

The latter—em-dashes—are usually roughly double or triple the length of the former (an en-dash).

The usage is different for each. (Wikipedia has a great article on them.)

While I'm not entirely certain about the first instance ('invitation- it will not...')... whether there should be a space on both sides of it, or neither side, or okay the way it is (i.e., with no space before, but with a space after)... I am reasonably sure it should be an em-dash (the longer one).

In the second instance: I believe it should be an em-dash (the longer one, again). However, I'm uncertain whether—having replaced it —there should remain spaces on both sides. This may have something to do with whether or not there are two of them surrounding a clause (i.e., to replace a pair of parentheses), or whether it's being used to replace something more akin to a colon.

Side note: Occasionally, when typing on a standard keyboard, two adjacent hyphens or en-dashes (see also footnote*) will be used, like so: --

However, this is not a true substitution for an em-dash, like so: —

Research needed (on proper spacing in various cases of em-dash usage, primarily). Man, syntax is complicated!

( footnote:<br> not even hyphens and en-dashes themselves* are the same... but sometimes, given the limitations of a standard keyboard or plain-er text typing program, the same character will used synonymously for both... however, it's generally frowned upon in more formal publications, I believe.)

Yet another concern about en-dashes, em-dashes, and the appropriate spacing for either (depending also on the purpose of their use).