What does the exclamation mark (!) means in Haploview output?

Question

[rimgubaev]

Hello everyone! I wonder if someone could explain what does the exclamation mark (!) means in the Haploview output in example below (see marker #31):

BLOCK 3.  MARKERS: 31! 32 33 34
3111 (0.655)    |0.646  0.000   0.003|
4433 (0.344)    |0.298  0.033   0.003|

It is also marked with triangle (see marker #31) when I visualize this using haplotypes tab in Haploview:

Tried to find answer in Haploview manual with no success. Thank you in advance.