How it is worked "String resultToSourceCode(const decode_results * const results)"

[MarkEvens]

  for (uint16_t i = 1; i < results->rawlen; i++) {
    uint32_t usecs;
    printf("%d, ", results->rawbuf[i]);
    for (usecs = results->rawbuf[i] * kRawTick; usecs > 65535; usecs -= 65535) {
      output += uint64ToString(65535);
      if (i % 2)
        output += ", 0,  ";
      else
        output += ",  0, ";
    }
    output += uint64ToString(usecs, 10);
    if (i < results->rawlen - 1)
      output += kCommaSpaceStr;            // ',' not needed on the last one
    if (i % 2 == 0) output += ' ';  // Extra if it was even.
  }

why this start from 1 instead of 0 And why 'kRawTick' default is 2 ?

[crankyoldgit]

why this start from 1 instead of 0.

because rawbuf[0] effectively contains junk (e.g. The number of ticks since we started listening for a signal till when we first saw the signal).
rawbuf[1] contains the first useful data of the actual message/signal.

And why 'kRawTick' default is 2 ?

Because is rawbuf[] is array of uint16_t to save space. Moving to uint32_t would cost twice the memory for next to no benefit.
A typical mark or space is capped by the kTimeout time. i.e. How long do we keep waiting for more of a signal before we give up.
That can be between 15ms or up to 90+ms. As we record the timing in usecs. that would be 15,000 to 90,000 usecs before the timeout is reached. 65,535 is the maximum value storable in a uint16_t. We need 17 bits to handle up to 130,541 which covers our 90,000 usec case. So, rather than use a uint32_t to store it, and waste twice the space, we reduce the timing resolution to 2usecs to fit it into a 16bit uint16_t integer.
e.g. a value of 45,000 in a rawbuf[] entry means, 45,000 ticks, and as tick is 2 i.e. kRawTick, we get 45,000 * kRawTick which means it was 90ms (or 90,000 usecs).

The TL;DR: is it's that value to save half the ram needed for the capture buffer at the slight reduction in timing resolution. The ESP doesn't have heaps of ram, we need to save it where we can. Timing down to 1usec resolution really doesn't matter for IR signals.

[MarkEvens]

Thank you @crankyoldgit