I think you mean 1.030,& that's a little low. Most noobs don't get the wort & top off water mixed well enough to get an accurate measurement. Pour both in the fermenter & stir roughly 5 minutes. That'll mix it well.
And the yeast won't change the gravity,just the sugars,etc in solution. As the sugar gets turned into co2 & alcohol,the solution's gravity gets lighter & the number on the hydrometer scale gets lower.