For prompt burst response images, the TLA is followed by an index number that identifies the GCN serial number of the alert of that particular type (as identified by the TLA, see Section A.1). This number will have at least four digits, but may have more. In the case of a simulated burst alert, the numbers will run sequentially from a number that is determined by simGCNalert, one number for each alert. For real GCN alerts, there is a unique number included in the packet array to identify the alert, and this number is passed on to the file name by the DAQ system.
In contrast, for most other types of images, including sky patrol, targeted observations, and burst follow-up images, the TLA
is followed by a nine-digit field which gives the coordinates of the center of
the field to four-digit accuracy. The Right Ascention is given as HHMM, and
the Declination is given by 
DDMM. Fractional minutes are rounded to the
nearest whole number.
Finally, dark images (drk) do not have coordinates. In this case, the four-digit identifying number following the TLA is the exposure time in tenths of seconds.