Everything, including the dividends in the ISA is tax free so no tax to pay and it does not count towards your limit.
In the GIA you have a limit of £2,000 so if you’re at or under that limit you have nothing to pay there either, so £0 liability. If you had £2,500 in your GIA, then tax would be payable on £500, being £2,500 received - £2,000 allowance.