Confused about the training data called img_kps

[zuixiaosanlang]

Hello,
I am confused about the data format img_kpts/<img_idx>.bin.
If i get a keypoint detect by SIFT，how can i get the values as:
affine = (-0.25711258, 0.52153266, -0.58181703, -0.78229898, -0.38566887, -0.53048758)
What laws are there between affine[0], affine[1], affine[3], affine[4] ?

Why the affine transformation matrix in <img_idx>.bin is not like this:
affine_mat[0, 0] = m_cos
affine_mat[1, 0] = m_sin
affine_mat[2, 0] = ptf[0]
affine_mat[0, 1] = -m_sin
affine_mat[1, 1] = m_cos
affine_mat[2, 1] = ptf[1]

i read the article GeoDesc: Learning Local Descriptors by Integrating Geometry Constraints，but still confused,

Thanks a lot for your help.

[luoqianchina]

Same question. Besides, in the article GeoDesc, equation(1) there is a σ' [-(kσ/2)sin(θ) (kσ'/2)cos(θ) y]. Is that correct? What does it mean? Or it should be σ? Thanks.