The Garden is a remodelation of DSRC after the flood dried and it get attached to the clock tower and master room of Ultiīs Castle (as known as excavation site).
Of course at this time Ulti had already made some changes on her castle.
We know that it is possible to refill the gas tank somehow from what we learn on DSRC.
But then the door unlocking sequence has to be done again.
This by itself is strange and indicates DSRC can time travel.
By the way,it is RSP (reserve steam pressure).Not reserve steam points.Sorry for that mistake.
Let me explain more.The Garden has some kind of GPS system.It was programmed to time-travel when it pass through certain regions.Of
course no one besides Odine (and probably Laguna) knows how to manually time-travel Garden.
Of course,it goes back to Ultiīs castle.The CLOCK TOWER was a primitive version of a time-machine.
The GPS system is also there.The big clock is a giant map.
The clocks central gauge represents FH.One of the pointers points toward Esthar(this one I donīt understand) and the other pointīs towards Edeaīs house.