james,
this is a parameter for maximum timing advance and it is in number of bit periods ranging from 0-63.
A TA of 63 corresponds to 35 km from the serving cell.
By setting a certain value of TA (Ericsson uses parameter TALIM), cell coverage is limited to a radius corresponding to that TA value ( TALIM=1 corresponds to 550m)
in a feature called Extended Range (Ericsson), MAXTA can be as high as 219.
m12