Transitional protection

Hi, I'm confused about transitional protection.
I migrated from ESA & child tax credit, to universal credit.

My universal credit payment is made up of;

Standard allowance; £400.14
Children; £292.81
Transitional protection; £428.15 (MONTHLY)

I do not have any housing help, so I believe my work allowance, once I start work, will be £684 per month.

If I work 25 hours at minimum wage, am I correct in assuming;

Minimum wage 25 hours: £12.21 x 25= £305.25 per week / £1322.75 per month

£1322.75 - 684 (work allowance) = £638.75
£638.75 x 0.45p = £287.43

£684 (work allowance) + 287.43= £971.43


So would my new monthly total be;

Work allowance+ earnings: £971.43
Standard allowance: £400.14
Children: £292.81

How would my transitional protection be affected?