Does Restoring my Mac from a Time Machine back up really mean I erase my destination drive?

I am faced with restoring my Mac after a crash using a Time Machine backup for the first time. It won’t start up after a series of crashes for some reason. I have recently cleared the Mackintosh drive and I now have my system booting up from a C Drive , a new SSD. So when I’ve followed the steps as described on Apple support sites I reach the following message...which no one seems to have mentioned.

so ...what do I do? It seems drastic to erase this new drive. Will it just be replaced by the last Time Machine back up or will I lose data.