I didn't understand you at first, but it was interesting to go back and forth later. In fact, it is a simple math problem, which should start from primary school.

25 b5 D6 Fe 1→25÷5-6 =- 1，

12d 13fe 1→ 12- 13 =- 1，

6B2F3→6÷2=3，

You got it? In fact, English letters only represent mathematical symbols, as can be seen from the above.

B is 0 °, D is-,F is =, E is negative, then

8 1B27D3DE 1F, just change it.

8 1 27-3-(-1) =1,so the answer is1.