Bitcoin's difficulty is set per epoch. Every block from a height divisible by 2,016 up to the block before the next such height carries the same target, encoded in its header's bits field. When an epoch's last block is found, the next block's target is computed from how long the epoch took against two weeks, the time 2,016 blocks would take at ten minutes each.
Within an epoch, a rise in hashrate shows up as blocks arriving faster, not as a higher difficulty. That is why the Network tab shows the current epoch's progress in blocks, with mempool.space's projection of the change: the next difficulty can be projected, but it is not known until the epoch ends.
The epoch is the unit in which the Gazette reports difficulty changes; the rule that sets each new value is defined under difficulty adjustment.