Description of problem:

In the description of the extraPartitionStart field in the Reference specifications for the image-based-installation-config.yaml manifest documentation the default value should be set to -40G instead of -40Gb. 

The suffix should be a single character from the following set [K,M,G,T,P], as the underlying sgdisk tool (please look under the -n, --new=partnum:start:end argument), which is used to partition the disk, expects a single character suffix.  In the OpenShift image-based installer we are also validating for a single character suffix.

PS. In the example YAML manifests in the same documentation page, this field is correctly defined as -240G .