Capital Gain Tax question of Chapter 14 (pg. no.90 example 2 of opentution note)

In short, question is, Annie who is disposing shares firstly with chargeable gain of 4,500,000 (qualifying for entrepreneur relief) and also a antique painting with chargeable gain of 100,000 in TY2017/18. She has b/f capital loss of 25,000 and has other taxable income is 18000 for same TY. We need to calculate CGT for 2017/18.

In this question, I deducted b/f capital loss of previous TY (25000) and AEA (11300) respectively from capital gain on antique painting. And get the taxable gain of 4,500,000 and 63,700 for shares and antique table respectively. Similarly, I calculate the unused BRB of 15,500 (33500- 18500).

Now kindly tell me why I cannot use the unused BRB for my taxable gain in antique table?

Answer in the opentution note is, (4500000*0.10=450000)+(63700*0.20)=462,740
But I get the answer as,
15500*0.10=1550
(63700-15500)*0.20=9640
4500000*0.10=450000
Total=461,190

Thank you.
Hope you got my point.