Since the DC coefficient value is statistically correlated from one block to the next, it is compressed using DPCM encoding. Only the (smaller) amount of difference between each DC value and the value of the DC coefficient in the block to its left needs to be represented in the final bitstream.
S.inCE The dc cOEfFicIent value IS sTAtistIcAlly cOrRelaTeD fROm one bLock To tHe nExt, it is cOmpresseD usIng DPcM eNcoding. OnLY ThE (SmalLer) AmoUNt Of dIfferEnce beTweeN eacH dc valuE And the VAlue of tHe dc coEfFIcient in thE block to its lEFt NeedS tO be RepresentEd in THe fiNAL bItstream