that is the time_frame variable itself.

try this out(copy/paste to sed and run)
Code:
#include <acknex.h>
#include <default.c>

var timePassed = 0;
var lastFrameDuration = 0;
var totalTimeFrame = 0;
var tickInMilisecs = 62.5;
FONT* arialMid ="Arial#14";
PANEL* infoPanel ={
	pos_x = 10; pos_y = 10;
	digits(0,0,"Total Frames:%.1f",arialMid,1,total_frames);
	digits(0,20,"time_frame in ticks:%.6f",arialMid,1,time_frame);
	digits(0,40,"time_frame in milisecs:%.6f",arialMid,1,lastFrameDuration);
	digits(0,60,"Total time frame in ticks:%0.6f",arialMid,1,totalTimeFrame);
	digits(0,80,"Total time passed in milisecs:%0.6f",arialMid,1,timePassed);
	digits(0,100,"Total time passed in secs:%0.6f",arialMid,0.001,timePassed);
	flags = SHOW;
}


void main(){
	fps_max = 30;//play with this
	while(1){
		totalTimeFrame += time_frame;
		lastFrameDuration = time_frame*62.5;
		timePassed += lastFrameDuration;
		wait(1);
	}	
}



Precision of the var type is debatable though it should be precise enough.


3333333333