Generic delta Saftey interval.

hi everybody,

I am trying to make a generic extractor -delta enabled.

i am confused about this --<b>upper limit and lower limit </b>in saftey interval.

for <b>time stamp, numeric pointer, date</b> fields.

could anyone kindly explain me what r these upper limit and lower limit and how they work in regarding this three field types.

i even read hw to generic delta document. but i got stuck with these two --terms.....

plz explain me in simple language. plz ihave even read in help i could only understand about saftey interval but not about upper limit and lower limit.

thanks and regards.