"Rest assured" is a phrase with an implied subject.. "you". So if you start out that sentence, "You rest assured" or "You may rest assured," then perhaps it will make more sense.
Another way of understanding that is to translate "(you) rest assured" as "I assure you."
Those darn implied subjects... they'll get ya if ya let 'em.
I don't know what the two Chinese words mean, but here's a fairly clear translated statement, I think.
Quote:
(You) Rest assured that the UK is in no way trying to produce ENCs outside its area os reponsibility;be that of its own waters or that of areas such as the South China sea where it is the designated producer nation of international chart(海图) covering areas of international waters and consequently has requirements placed on it by WEND principles.
You may rest asssured (that is: you do not need to worry) that the UK is in no way (i.e.: it is not) trying to produce ENCs outside of its area of responsibility; be that of its own waters (i.e.: whether that area is its own waters) or that of areas (or of other waters) such as the South China sea where it is the designated producer nation of international chart(ers?) covering areas of international waters and consequently has requirements placed on it by WEND principles.