What value to use for shares bought over time for CGT threshold

I’ve bought shares in the company I work for via 2 share save schemes at 2 different prices. Both are fully mature and beyond the tax window. Since then there has been a further rights issue which diluted the value of the shares market price. In the rights issue for each 10 shares owned I could buy 3 further shares at 32p. I took up this offer to offset the dilution effect. I now have no idea how to calculate the value I should use to work out how many I can sell at the market rate and stay below the CGT threshold. Any advice / guidance.

Hi,
You can see guidance here:
HS285 Share reorganisations, company takeovers and Capital Gains Tax (2024)
Thank you.