PVS-Studio warning V568 for Asterisk

static int redirecting_reason_build_data(....)
{
  ....
  if (datalen < pos + sizeof(data[0] * 2) + length) {       //<==
    ast_log(LOG_WARNING, "No space left for %s string\n", label);
    return -1;
  }
  ....
}

This suspicious code was found in Asterisk project by PVS-Studio static code analyzer.
Warning message is:
V568 It's odd that the argument of sizeof() operator is the 'data[0] * 2' expression. channel.c 8853

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