not bad for a first sub!
This is pretty tight, and I like the melody a lot.
However, what made me give you a 7 as opposed to an 8 is that this song suffers from some technical issues, mainly that when things get too loud, it starts to crackle and pop, which is pretty jarring.
It's important to fix this problem early in your musical career!
If you use FL Studio, this can be solved by turning down the main volume, or turning down the volumes of the various channels causing the cracking. Filter effects are important too.
If you're not using FL, than the above still generally applies, but obviously with the terminology of the program you are using.
You're off to a good start- keep up the good work!