There are several ways you can find lot sizes and property dimensions in AUTOPROP.
The lot size can be found in the following places:
Properties Table / Load Data (Paragon and VREB users)
Tax Report (Paragon and VREB users)
Property dimensions can be found in the Full Report under the municipality's GIS, where available.
Create a Full Report on the property
Click the green Adjust Report Contents button
Choose the lot dimensions/property dimensions option in the Municipality's GIS data source
See below an example for Vancouver: