Yes.

Once you reached Silver, a brand new period - the "Upgraded Fixed Membership Period" - commenced.

In that "Upgraded Fixed Membership Period", which commences on the day after you were upgraded to Silver, your first "target" is to requalify for Silver by earning another 300/400* tier points within 1 year. If you reach or exceed 300/400*, congratulations! That guarantees a second year of Silver.

To get to Gold, though, you must reach a total of 800/1000* tier points; all of which must have been accumulated while you were Silver. (The 300/400* that got you from Red to Silver cannot also count to maintain a 2nd year of Silver or to help get you to Gold).

*as you know, up until 1 April 2023, 300 tier points (rather than 400 tier points) were required to get to/maintain Silver. Once you had achieved Silver, a new period (of maximum 1 year) commences, during which a further 800 (rather than 1000) tier points would have got you to Gold, if achieved prior to 1 April 2023. So, in total, you would have needed 300+800=11000 tier points to get from Red to Gold. Currently, the corresponding figures are back to the normal amounts; it takes 400+1000=14000 tier points to get from Red to Gold, so long as these are all separately achieved within the corresponding (and different) time intervals.

Because it would be far too easy to earn status that way!