im not sure if this goes here but how do u set the grav to a high and low /....??

[20:53] <taffjr1234> hello
[20:53] <Shin-Ryuu> yo
[20:53] <taffjr1234> i need help
[20:54] <Shin-Ryuu> ?
[20:54] <taffjr1234> i need to get the grav so i can walk
[20:54] <Shin-Ryuu> 0 0 -30
[20:54] <taffjr1234> thx
[20:54] <taffjr1234> but i wont work
[20:55] <Shin-Ryuu> you do /set gravity 0 0 -30
[20:55] <Magix> ./set gravity 0.00 0.00 -30.00
[20:55] <Shin-Ryuu> rest is for you to learn
[20:55] <Magix> and then open up singleplayer again
[20:55] <taffjr1234> ye done
[20:55] <Magix> and it wont work?
[20:55] <taffjr1234> so its /set grav 0 0 -30
[20:56] <taffjr1234> nop#
[20:56] <Magix> 0.00 0.00 -30.00
[20:56] <Magix> and gravity not grav
[20:56] <taffjr1234> ahh
[20:56] <taffjr1234> it works thanks