Medical expenses - meals. Are these reimbursed at $51 or is that the portion that is deductable?

Yes, This is the amount you will claim for meals per day that is deductible.

As per CRA- 

• You need to have traveled more than 80 km for care to claim meals with the CRA. Just like vehicle costs, you can choose the use of the detailed method or the simplified method. 
• To use the detailed method, you tally the actual cost of each meal. 
• If you choose the simplified method, you may claim up to $17 per meal, up to a maximum of $51 per day, including sales tax. 
• Whether you choose the detailed method or the simplified method, be sure to keep those receipts.