This is related to why there is always a buffer of at least 1000ft between the Transition Altitude and the Transition Level.

If you are at 4000ft and want to climb to FL070, then once you cross the TA at 5000ft, you set QNE and climb until tour altimeter reads 7000. It does not matter whether the altimeter briefly changes to 4500 or 5500 at the instant you cross the TA since both are below the reading you’re climbing to.

Ditto for setting QNH when descending through the TL.

This is related to why there is always a buffer of at least 1000ft between the Transition Altitude and the Transition Level.

If you are at 4000ft and want to climb to FL070, then once you cross the TA at 5000ft, you set QNE and climb until your altimeter reads 7000. It does not matter whether the altimeter briefly changes to 4500 (or 5500) at the instant you cross the TA since that is below what you’re climbing to.

Ditto for setting QNH when descending through the TL.