How many external monitors does the iMac 27" with 5k display support?

Specs indicate just 1. Has anyone connected more than 1 monitor successfully? How many can you connect in total?

The Late 2015 iMac 5K with AMD 395X can support two external 4K (UHD) displays (at the full 3840x2160 res) with the builtin iMac display set to 5120x2880 FYI. This is the configuration that I am currently running (with 10.11.2), using two LG 27MU67 displays attached via DisplayPort-to-miniDP cables on each of the iMac's thunderbolt ports.

From Everymac…

In addition to the internal display, this model can support an external display up to 3840x2160 via Thunderbolt 2 (4K UltraHD). Third-parties have discovered that it also can support two simultaneous 27-Inch Thunderbolt displays at 2560x1140 each in lieu of a single UltraHD display.

I'm tempted to think that 2560x1140 is a typo & ought to be 2560x1440