Make sure you don't get off at Hauptbahnhof Ost station
There is only one station in Munich called Hauptbahnhof. That is the main station, west of downtown. The east station is called München Ostbahnhof, or simply München Ost.
Excuse my confusion, but looking at the departure board for Munich Hbf, next Sunday, the only 11:28 train I see is an ICE to Dortmund via FRA and Köln. The only 12:17 train I see is an EC in the opposite direction, Klagenfurt via Salzburg. Where are you trying to go?
My biggest concern would be that if you are coming from the US, there is a likelihood that the plane will arrive too late to make even the 12:17 train.
Update: looking farther out on the calendar, I see, for May at 11:28, a RailJet to Budapest via Salzburg.
If you are going to Salzburg or beyond, the EC (but not the RailJet) stops on it's way out of Munich at Munich East (München Ost) Bahnhof, which is only 31 minutes from the airport on the S8.
Note, that in the MUC S-Bahn station, the S1 is shown as going to Ostbahnhof, because that is its final destination. But the S1 takes longer to get to Ost than the S8, which comes into Munich from the east side, stopping at Ostbahnhof, then going through town and to the west to its final destination.
Also looking at the routing for those two trains, the last common stop is at Salzburg, so you must be going to Salzburg or someplace closer. Instead of buying an expensive full fare ticket of one of those trains, or a risky Savings Fare ticket, just buy a Bayern-Ticket at the airport S-Bahn station, go to Ost, and board one of the hourly Meridian regional trains to Salzburg. It will only take about a half hour longer at most and you can take the next train out, no matter when you arrive.