8L Mash Gravity before sparging with 4L = 1.055. Keep mashing till this gravity reached 4L Sparge with hot tap water Gravity after sparging = 1.043
Based on boiling 12.00 gallonsliters at 1.043 for 30 minutes, this will decrease your wort by 2.00 gallonsliters, bringing your after boil OG to 1.050. You wanted an OG of 1.049. It looks like it will be over.