Writing 300+ words won't be seen negatively....if you've done well with those 300 words ,you are sure to score well...
even I had done 300+ and got 7.5 despite pathetic (almost non legible ) handwriting...I hadn't wrote anything for close to 10 years with pen (except occasional form fillings as part of daily life..) and all I did was 2-3 days and 10 odd practice essays...I was horribly disappointed at the end of my writing session looking at my paper...and was hoping to score less than 5...
I got 7.5 only because of writing enough and bit extra...
I got 8.5 for other 3 sections and overall 8.5 too by God's grace...