What does my Shinkansen ticket say?

Here is a Shinkansen ticket:

I understand most of it, but the line below the "to" and "from" feels contradictory to me. It says that

7月23日から4日間 4 days starting from July 23

and also that

7月23日当日限り有効 valid only for July 23

If the ticket is valid only for July 23, what is the "4 days starting from July 23" doing here? Is it valid for all 4 days or just 1?

In addition, apparently the 11880 yen ticket is split into 7340 and 4540 yen. The former is marked 乗 and the latter 特. What does this mean?