public synchronized long append(
            OptionalLong requiredBaseOffset,
            LocalBatch batch
        ) {
            long nextEndOffset = prevOffset + batch.size();
            requiredBaseOffset.ifPresent(r -> {
                if (r != prevOffset + 1) {
                    throw new UnexpectedBaseOffsetException("Wanted base offset " + r +
                            ", but the next offset was " + nextEndOffset);
                }
            });
            log.debug("append(batch={}, nextEndOffset={})", batch, nextEndOffset);
            batches.put(nextEndOffset, batch);
            if (batch instanceof LeaderChangeBatch) {
                LeaderChangeBatch leaderChangeBatch = (LeaderChangeBatch) batch;
                leader = leaderChangeBatch.newLeader;
            }
            for (LocalLogManager logManager : logManagers.values()) {
                logManager.scheduleLogCheck();
            }
            prevOffset = nextEndOffset;
            return nextEndOffset;
        }
The initial max read offset which LocalLog instances will be configured with.
metadata/src/test/java/org/apache/kafka/metalog/LocalLogManager.java