http://techdocs.altium.com/display/ADOH/Design+Rule+Checking
http://techdocs.altium.com/display/ADRR/PCB((Design+Rules+Reference))
Elecrow Design Rules
Silkscreen
Min Width 0.15mm / 6mil
Min Height 0.8mm
Vias and Traces
Min Clearance 0.15mm / 6mil
Min Via size 0.3mm / 12mil
Min Ring size 0.15mm / 6mil
Max Drill size 6.3mm / 248mil (otherwise holes will be milled)
Min Trace width 0.15mm / 6mil
Min Hole-to-Hole Clearance 0.254mm / 10mil