No (as you now know) the £9000 per annum you get from a defined benefit pension scheme is calculated from what 1/49 (or whatever) of your salary has been every year for 13 years all added together.
So for simplicity sake
If your salary was around £34,000 a year every year for 13 years then 1/49 of that salary would be about £693 per year
So your annual pension after 1 year of work would be
£693
After 2 years of work your annual pension would be £1,386 (£693 + £693)
3 years
£2,079 per annum
4 Years
£2,772 per annum
5 Years
£3,465 per annum
6 Years
£4,158 per annum
7 Years
£4,851 per annum
8 Years
£5,544 per annum
9 Years
£6,237 per annum
10 Years
£6,930 Per annum
11 Years
£7,623 per aannm
12 years
£8,316 per annum
13 years
£9,009 per annum (13 x £693)
Of course people don't earn the same wage every year for the rest of their lives so a different amount will get added to the accumulated annual amount every year - but this is just an example.
Almost entirely separately to that is your employee contributions
If your employee contribtion to your pension is e.g. 6.7% of your salary then on £34000 you will have been paying what is essentially a £189 a month 'subscription' to be able to access your annual pension of £9009 a year in the future based on only working/subscribing for 13 years.
On £34000 a year your £189 a month 'sub' from your salary (£2268 per year) will have meant you will have been operating at a loss for the first 3 years as your annual subscription to the scheme fot those years was more than your annual future pension will be.
But after year 4 the amount you will get back as an annual pension in the future is above what you are paying in annually from your salary as a sub currently and by year 13 you are only paying £2268 a year as a subscription from your wage whilst in work in return for £9009 a year hard cash pension when eventually you retire if you've only worked 13 years.