The reason is that the value sent to the split function is not a 16 bit number as it should be (to be splitted into two bytes), but an I32. It's the constant (50) that the angle is multiplied by that forces the type from U16 to I32, just change the type of that constant.
LabVIEW tries to indicate all this to you by placing small grey coercien dots at the terminals. If you look there are lots of them, e.g. on the hi and low byte indicators, this shows that the output of the split is not a byte.