Why does "rrdtool fetch" not match cacti's csv export?

[smokingbug72]

Hi all :

I am a Taiwanese and my English is not very well,Please forgive me.
I have met a strange problem on data export. I need to export rrd data to mysql in my company for some backend using.
I found some resources from network and try to export it. At last, I can export the rrd data to Mysql DB and create table automatically.
But I also found that my data from rrdtool fetch value is not the same as Cacti export csv value, that let my data become useless...

As Cacti export csv is like below : (http://10.7.15.100/cacti/graph_xport.ph ... 1418641259)
2014/12/15 18:24 1.52E+05 2.63E+06
2014/12/15 18:30 1.40E+05 2.40E+06
2014/12/15 18:36 1.39E+05 2.03E+06
2014/12/15 18:42 1.05E+05 1.73E+06
2014/12/15 18:48 1.30E+05 2.02E+06
2014/12/15 18:54 1.71E+05 2.48E+06
2014/12/15 19:00 1.55E+05 2.28E+06

As my rrdtool fetch is like : (/opt/rrdtool-1.4.2/bin/rrdtool fetch -r 300 tw_7f_fortigate_600c_traffic_in_691.rrd AVERAGE)
1418635800: 3.1237308966e+04 4.8432333696e+05
1418636160: 3.0381278535e+04 4.0851701757e+05
1418636520: 2.8533412489e+04 4.6470529025e+05
1418636880: 2.6009519048e+04 4.6370968651e+05
1418637240: 2.8387116314e+04 4.4493911944e+05
1418637600: 3.0714455990e+04 4.6786270906e+05
1418637960: 2.6155861336e+04 4.3903226596e+05

I use the same Condition and rrd, but get the different result, please give me a hand , thx!!

[smokingbug72]

I do not know if anyone had the same problem and solve it.
Please provide some ideas or comments to me.
Thank you very much ~

[smokingbug72]

Seeking experienced friends to share, thanks!!