For T1, it looks like they want you to find the midpoint between the sprocket and chainring, pull the chain as far apart as it will go and measure the outside dimension. For T2, use the same midpoint but squeeze the chain in and measure the outside dimension. Their illustration seems to be a bit exaggerated which has lead to some confusion for you. T1 will likely be a good bit smaller than the chainring diameter and T2 will be a good amount larger than the sprocket diameter, unless your chain is really loose.