To just explain the bottom line, and include mods, that is probably the shortest way of putting it.
Except, if nit-picky about a dictionary statement, one could differentiate "doubled" a tiny bit more.
a) The character gets a buff after the first weapon hit. As long as this buff is active/charged, the character gets bonusses of all parameters. The bonusses are appropriate to the charged level of the skill itself and the skilled levels of the modifiers.
b) All offensive parameters of the base skill and modifiers also appear full strength on the weapon attack. Meaning the offensive parts of modifiers are doubled with the first charge, and those of the skill at full charge.
Is anyone still reading this?
Anyhow, I think that should be sufficient.