I only count one spider?
but your answer is we can't answer that for reasons above, honestly if what your shooting for is axanthic spider, breed a spider het to an axanthic, that gives you a 25% chance for spider axanthic. 12.5% if you breed a spider het to a het. keeps it simple.
tho if you do end up with some sort of spiderxspider pairing, please post as much detailed info as possible.