Split can be something other than 50/50. For example, when talking about profit share, you could agree on an 80/20 split. But if you don't explicitly state the split, I would expect it to be closer to a half share.

What does split into mean?

split into (number or fraction)

1. To divide cleanly or evenly into some smaller number of things. The mirror toppled over and split into three nearly identical shards. ... To divide someone or something cleanly into some number or fraction of a whole.

What does splitted mean?

: to break apart or into pieces especially along a straight line. : to separate or divide into parts or groups. : to separate or divide into groups that disagree.