What does the "@" symbol in the Running Applications/Services mean? What does the "@" symbol in front of the time given in the right column of Running Applications/Services mean?

See screenshot below.

Phone: Samsung Galaxy S4 (GT-I9505)
OS: 4.2.2


Screenshot (click image for larger variant)
It means that the process has been running longer than 99 hours, 99 minutes, and 99 seconds. It's a formatting bug. 

The second hour digit, after reaching '9', will simply continue with the next characted from the ascii alphabet: 

0123456789:;&lt;=&gt;?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~


Where in this case ':' means 10, ';' means 11, '&lt;' means 12, etc.

For example, '&lt;5:12:34' means 125:12:34 and '?5:12:34' means 155:12:34.

It's fixed in Android 4.3

The Related bug report is here: http://code.google.com/p/android/issues/detail?id=41401