The information provided pertains to the accounting treatment of share-based compensation expense in relation to stock options granted to the directors. When estimating the expense related to share-based payment plans, such as stock options, adjustments are made based on the expected number of options that will vest. In this case, with two directors leaving the company in 2019 and the revised estimate suggesting that only four out of the initial six directors will remain with the company until 31 December 2020, it implies that the expected vesting of the options might change.

However, the specific numbers provided in the question—250,000 for expense in 2019 and 750,000 for cumulative expense, or 350,000 for expense in 2019 and 850,000 for cumulative expense, or 300,000 for expense in 2019 and 800,000 for cumulative expense—do not directly correspond to the number of options or the specific details of the share-based compensation plan. These figures likely represent the accounting estimates of the fair value of the options granted, amortized over the vesting period.

Without more detailed information about the original grant, vesting schedule, and the fair value calculations, it's not possible to determine the exact figures for the expense in 2019 and the cumulative expense that will be shown in the accounts. However, based on the revised estimate, it can be inferred that the expense for 2019 would be lower than it would have been if all six directors had stayed, and the cumulative expense would reflect this adjustment as well.

To provide a precise figure, we would need more data, such as the grant date fair value of the options, the vesting schedule, and the number of options granted initially and how many are now expected to vest. Nevertheless, given the context, it seems reasonable to assume that the expense for 2019 would be lower than the previous year's expense, and the cumulative expense would also be adjusted downward due to the revised vesting expectations.

In conclusion, without the specific details of the share-based compensation plan, it's not possible to definitively determine the exact numbers for the expense and cumulative expense for 2019. However, the information provided suggests that the expense for 2019 would be less than the previous year, and the cumulative expense would also be adjusted accordingly.