For half of the cupcakes, Stephanie wants to use 1 candle each. Since half of the cupcakes is 24/2 and she plans to use 1 candle each for this half of the cupcakes, Stephanie needs (24/2)*1 = <<24/2*1=12>>12 candles for this half of the cupcakes.
For the other half of the cupcakes, Stephanie wants to use 2 candles. Therefore, she will need (24/2)*2 =<<24/2*2=24>>24 candles for this half of the cupcakes.
Because Stephanie needs 12 candles for half of the cupcakes and 24 candles for the other half, she needs a total of 12+24=<<12+24=36>>36 candles.
Since Stephanie needs 36 candles to decorate all the cupcakes and she currently has 30 candles, Stephanie needs 36-30= <<36-30=6>>6 additional candles.
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