using pwmWrite.h for controlling led and servo

[oogre]

Hello,

I'm a bit confuse,
about this function

void Pwm::wr_ch_pair(int ch, uint32_t frequency, uint8_t bits) {
  mem[ch].frequency = frequency;
  mem[ch].resolution = bits;
  if (ch % 2 == 0) { // even ch
    mem[ch + 1].frequency = frequency;
    mem[ch + 1].resolution = bits;
  } else { // odd ch
    mem[ch - 1].frequency = frequency;
    mem[ch - 1].resolution = bits;
  }
}

I cannot see the purpose of using 2 mem channels to store info about only one servo motor,
and why don't you mark this channel +1 or -1 as used ?
It's blocking me to use properly servo and pwm at the same time