"I tried with size but it did not work!"
The size of a structure is completely independent of how many fields it has.
To count how many fields a structure has you can use this (where S is the structure):
"the result should be 14!"
Judging by your screenshot the structure has 14 elements, which you can count very simply:
Your screenshot does not show how many fields your structure has, but given that you expect the result to be 14 and that the structure (apparently) has 14 elements, it seems very likely that you are mixing up fields and elements of the structure. How many elements a structure has (and more specifically what sizes the dimensions have) is independent of how many fields a structure has (which is what you asked about).