To be honest, at 70kg you are really going to struggle until you are more advanced.
If you absolutely must go short then something like this will be better
http://www.surfdome.com/surf_series_surfboards_-_surf_series_fun_surfboard_-_6ft_8-43331 (and the 7ft2 even better)
This one would be possible as well
http://www.surfdome.com/oshea_surfboards_-_oshea_mini_mal_epoxy_eps_surfboard,_blue_-_7ft_2-29810Thats just looking at the website you nominated; there will be better boards than that elsewhere.
Also, by the way, the board dimensions on that site dont match the dimensions on the NSP site. So I would do a bit more research rather than just look at that site.
But, really, read up on the reasons why bigger boards are better for beginners and the issues with starting short; then knowing the risks make up your own mind. Just look around this forum especially under 'surfboard advice' ('surfing lessons for all'). Either way, get the biggest board (length, width and thickness) you are prepared to get.