[FFmpeg-user] understanding pts

[Sense]

I have a video file with 30 frame rate. As far as I know, the frames PTS sequence(if started from 0) should be 0, 3000, 6000, 9000 and so on. But when I show frames information with the following command  ffprobe -i seconds.mp4 -show_frames, the PTS sequence is something like the following:
ffprobe version N-45589-gb6a0b8b-   http://johnvansickle.com/ffmpeg/    Copyright (c) 2007-2014 the FFmpeg developers
  built on Aug 28 2014 02:30:32 with gcc 4.8 (Debian 4.8.3-9)
  configuration: --enable-gpl --enable-version3 --disable-shared --disable-debug --enable-runtime-cpudetect --enable-libmp3lame --enable-libx264 --enable-libx265 --enable-libwebp --enable-libspeex --enable-libvorbis --enable-libvpx --enable-libfreetype --enable-fontconfig --enable-libxvid --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-gray --enable-libopenjpeg --enable-libopus --disable-ffserver --enable-libass --enable-gnutls --cc=gcc-4.8
  libavutil      54.  7.100 / 54.  7.100
  libavcodec     56.  0.101 / 56.  0.101
  libavformat    56.  3.100 / 56.  3.100
  libavdevice    56.  0.100 / 56.  0.100
  libavfilter     5.  0.103 /  5.  0.103
  libswscale      3.  0.100 /  3.  0.100
  libswresample   1.  1.100 /  1.  1.100
  libpostproc    53.  0.100 / 53.  0.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'seconds.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf56.4.101
  Duration: 00:00:02.00, start: 0.000000, bitrate: 313 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 560x320, 307 kb/s, 30 fps, 30 tbr, 15360 tbn, 60 tbc (default)
    Metadata:
      handler_name    : VideoHandler
pkt_pts=0
pkt_pts=512
pkt_pts=1024
pkt_pts=1536
pkt_pts=2048
pkt_pts=2560
pkt_pts=3072
pkt_pts=3584
pkt_pts=4096
pkt_pts=4608
pkt_pts=5120
pkt_pts=5632
pkt_pts=6144
pkt_pts=6656
pkt_pts=7168
pkt_pts=7680
pkt_pts=8192
pkt_pts=8704
pkt_pts=9216
pkt_pts=9728
pkt_pts=10240
pkt_pts=10752
pkt_pts=11264
pkt_pts=11776
pkt_pts=12288
pkt_pts=12800
pkt_pts=13312
pkt_pts=13824
pkt_pts=14336
pkt_pts=14848
pkt_pts=15360
pkt_pts=15872
pkt_pts=16384
pkt_pts=16896
pkt_pts=17408
pkt_pts=17920
pkt_pts=18432
pkt_pts=18944
pkt_pts=19456
pkt_pts=19968
pkt_pts=20480
pkt_pts=20992
pkt_pts=21504
pkt_pts=22016
pkt_pts=22528
pkt_pts=23040
pkt_pts=23552
pkt_pts=24064
pkt_pts=24576
pkt_pts=25088
pkt_pts=25600
pkt_pts=26112
pkt_pts=26624
pkt_pts=27136
pkt_pts=27648
pkt_pts=28160
pkt_pts=28672
pkt_pts=29184
pkt_pts=29696



Is this correct? How to convert time in PTS to time in seconds?