I can't mimic the exp_len.txt with my own data

[HeeseonPark]

I wonder if I can make data like "exp_len.txt" of data directory.
Could anyone explain me what the each column mean?

UBL5 NM_024292 519 23.1125
PHF1 NM_024165 2294 2.13837
PALM2 NM_053016 9478 0.262067
XKR4 NM_052898 3907 0.25588
CSMD2 NM_052896 13108 2.5265
YME1L1 NM_139312 4025 2.29835

I'd like to know the meaning of the third (ex. 519, 2294, 9478,,,) and fourth (ex. 23.1125, 2.13837,,,) column.
Please let me know the meaning of each column !!

Thanks,
Heeseon Park.