You were right! Although my original partition had a block with 0 size (which I took as a base), I couldn’t set it again after typing the original numbers… Who knows why? 
Anyway, I set my partitions as follow and it worked fine! Now I have plenty of room for my Java machine and other stuff!
[code]
AT!UNLOCK=“A710”
OK
AT!APPPARTCHG=768,50,19000,384,160000,300,10000,383,71000,1
OK [/code]
After erasing and flashing…
Filesystem Size Used Available Use% Mounted on
/dev/root 156.8M 132.8M 24.0M 85% /
/dev/mtdblock4 72.0M 2.3M 69.7M 3% /mnt/flash
/dev/mtdblock3 10.5M 1.5M 9.0M 14% /mnt/legato
/dev/mtdblock5 5.3M 2.8M 2.4M 53% /mnt/userrw
unionfs 72.0M 2.3M 69.7M 3% /etc
unionfs 72.0M 2.3M 69.7M 3% /data
Thank you very much!!!