Missing data field

[J_Ruck]

I am trying to interpolate some data, however, when I go to input the data set there are multiple columns of data missing in the 'Data Field'. What would cause this to happen? 

The images below show a column of data I would like to use, but only one column of data from my layer pulls up in the geostatistical wizard. 

[DanPatterson]

A field that is left-justified by default is a text field even though you think it contains numbers.  You will have to add a new field and use the field calculator to convert the "text" to numbers.