Hi,
looking at the R22 charts in the POH which is on my desk, my interpretation is that there are two types of temperature lines on each chart.
There is a dashed line and there are unbroken lines.
The dashed line indicates a standard day temperature. This is what your instructor is probably talking about. During certification a lot of the performance calculations are referenced to a "standard day" set of conditions. They then workout from there what effects temperature has on the performance. Infact if you have a look at the introduction to section 5 of the POH it states:
The performance data presented in this section was obtained under ideal conditions. Performance under other conditions may be substantially less. Hover performance data was obtained with carburettor heat off.
The unbroken lines are temperature lines. The higher temperature lines are closer to the bottom of the chart, which follows from higher temperature = less performance for the same weight.
If your instructor still has problems with this then I suggest that he goes back to school for a while until he understands what the charts actually state.
Tinkicker....