extensometer data

I have been trying to use an axial extensometer on instron 5560. The
data that I get from using the extensometer shows as "strain 1%" is 20
times more than the actual data that I expect ( the data from
crossheads moving which is "tensile strain").
How can I change that?
The gauge length of extensometer is 1 inch. The gauge length of the
crossheads is about 1.5-2 inches.