Why is downtime greater than uptime?

Question

linux

Here:

$ uname -a
Linux HOSTNAME 2.6.31.14_7820 #22 SMP Wed Sep 21 16:29:23 CST 2011 armv6l GNU/Linux

$ uptime
 06:15:21 up 37 min,  X users,  load average: 0.19, 0.37, 0.49

$ cat /proc/uptime
2286.49 3189.43

Although proc(5) says
/proc/uptime
This file contains two numbers: the uptime of the system (seconds), and the amount of time spent in idle process (seconds).
Info about the processor in Linux (Transmission is constantly running):

$ cat /proc/cpuinfo
Processor       : ARMv6-compatible processor rev 5 (v6l)
processor       : 0
BogoMIPS        : 299.00

processor       : 1
BogoMIPS        : 299.00

Features        : swp half thumb fastmult edsp java
CPU implementer : 0x41
CPU architecture: 7
CPU variant     : 0x0
CPU part        : 0xb02
CPU revision    : 5

Hardware        : Oxsemi NAS
Revision        : 0000
Serial          : 0000000000000000

Answer 1

Because idle time is considered in total for each core of the processor.
Here's an example - booted up an hour ago, did nothing all this time.
Uptime - hour. And the idle time for a 4-core processor is 4 hours.