Leave Travel Allowance carry over to the immediate calendar year from current block

Hi Sree, Hope you are doing well. I have been following your blog for the last 3 years. Its awesome and kudos for your great service to help people. I have a query here on LTA claim. On the current block 2014-2017, I have not claimed any LTA exceptions. I spent a huge amount(60K) which covers under LTA in 2017.  But by mistake, I have opted for a small amount(15k) of LTA as a part of FY17-18 flex pay. (Now I can't go back to my employer and revise it). So, rather than claiming this 15K in this current block, I am planning to carry forward this exception to the next immediate calendar year by without claiming this 15K in this current block. So that I will get three LTA exceptions in the next block of 2018-2021. As I have not utilized any LTA exception in the current block, is it possible to carry forward the two exceptions from the current block to the next block? If so, it will enable me to get four LTA exceptions in the next block. I know it is not feasible. But I would like to confirm the things from the experts. If I can't claim four LTA exceptions in the next block, then I things it makes sense for me to go ahead and claim one of the LTA exceptions in the current block with this 15K and utilize one more LTA exception as a carry forward to the next block. Please correct me if I am wrong and provide your valuable ideas. If I claim one exception out of available two options in the current year itself, is it possible to carry forward the remaining one LTA exception to the next block? Thank you so much.