A complete, dated admission and departure history supported by documents, plus every approval notice and visa covering the L period. Without it, any discussion of remaining time is guesswork. Counsel can then apply the limits and any exceptions to that individual record.
The chronology is the whole exercise
General statements about maximum periods of stay are easy to find and impossible to apply without the person's own dates. Time spent outside the country, movement between L-1A and L-1B, and periods with related entities can all matter to how a case-specific analysis reads. Assemble the record as evidence rather than as a memory aid, and flag any period you cannot document so counsel knows exactly where the uncertainty sits.
Two points are worth stating explicitly before the chronology is built, because they explain why it matters so much. L-1A stay is capped at seven years in total and L-1B at five, and time held in one of those classifications counts toward the applicable limit rather than resetting on a new approval or a change of employer within the group. Separately, time spent outside the United States may affect how the maximum is counted in an individual history, which is a case-specific legal question rather than an arithmetic rule anyone can apply from a summary.
Both mean the printed dates on a current notice describe a period of admission, not the person's remaining room. Hypothetical example: a worker at a contract research organisation assumes three years remain because the current notice runs that long, and the chronology shows a considerably more complicated position that counsel can only assess from the underlying dates.