many different factors influence the safety factor when using a particular size kite in given wind ranges. With everything else being equal, the 2 main considerations are riders ability and wind density, i.e. the colder the wind is the more power it will have at the same wind speed.
The manual considers a 12m safe for an expert rider (80kg) from 13-24 knots. Riders who are significantly heavier, or lighter should use, for a given wind speed range, kites that are one size bigger or smaller respectively.
IKO instructors manual states that when teaching someone 30kg heavier than yourself use extreme caution. Therefore 20kg is significantly heavier.
Living in VIC(??? or is it saudi arabia

) the 14 was a good choice and you have the wind ranges of your new kite pretty good, but 25 knots should be the maximum limit as gusts can be up to 40% stronger thant the average wind speed!
Cheers DPH