Texas Instruments CBL Manual Book page 66

Triggering with Prestore
How It Works
Due to sampling times and the input signal, the first sample after the
trigger point may not occur at the exact trigger point. The sample taken
could be up to one sample time after the trigger point.
If a nonzero prestore is requested, the length of the list returned by the
CBL may not equal the number of samples requested. The CBL
guarantees that the number of poststore points derived from the
prestore parameter will always be taken; however, the number of
prestore points varies depending on the timing of
occurrence of the trigger event. There may not be enough time between
these two events to collect all the prestore samples requested.
Because the some calculators, such as the TI-82, only returns lists up to
99 elements, determining the actual length of the list collected by the
CBL is difficult unless the number of samples requested is 99 or less. If
CMD5 is used to change the data range, the T computed on the previous
page could be outside the list retrieved from the CBL.
66 CBLé System Guidebook
(Continued)
CMD3 and the