What do the +X numbers at the end of trainer names mean

It appears that Hourglass comes as close to "TAS"ing for Windows as it can possibly be done nowadays. Here's a "test run" by diggidoyo of the first two levels of Super Meat Boy.

The author comments:

I can't get the audio to dump, and save states crash the game. I'm sure it's because of the multi-threads (can't run with this disabled). I only used frame advance, but the later levels will need save states to be efficient. Still, frame advancing brought the times to attractive low numbers.

Thus, while it's not quite ready for serious tool-assisted speedruns, it might just be enough tools to be effective as an anti-frustration solution. (It appears, however, that it conflicts with Steam.)

To directly answer your question, 'ss' is a shorter version of 'miss'. In certain regions, they differentiate between this and "MIA", which is meant to refer to a specific opponent whose location is not known rather than a lane with missing people.

From a forum post:

SS (ss bot, ss bot 2, etc...)

Miss, the enemy/enemies are missing from lanes. Normally only called during the laning phase of a game. The lane from where the enemy is missing can be (and should be) said after ss, and a number of enemies missing can be inserted after that; So "ss top 2" simply means that 2 enemy champions that were laning top are now missing, and your teams mid should be extra careful (as should you).

MIA (mia noct, mia shaco, etc...)

Missing in action, an enemy champion is missing in sense that your team does not know his location. For when you are going into a teamfight and only see 4 enemies ahead of you there is a good chance that Fiddlesticks is going to jump to you soon from his hiding place, for example.

On North American servers, people tend to use mia for both purposes:

• mia mid
• mia shaco