You can use your 19a value from Ancestry in 19/394 (it is DYS value 19, but sometimes referred to as 394). I would leave dashes as dashes and not change them to nulls. I assume you are probably referring to GATA H4 for the "subtract 11"? That is actually not correct anymore (probably an old conversion chart). You should subtract one from your Ancestry value (so it will be 11 for you).
Happy yDNA matching!