Change from standard to compact chainset

[KneesUp]

Just checked my rear mech and info is as follows. Shimano RD 4500 GS Medium cage. Does this help?

Model Number RD-4500-GS
Series TIAGRA
Cassette Compatibility 9-speed
Maximum Sprocket 27T
Minimum Sprocket 11T
Maximum Front Difference 22T
Total Capacity 37T