Yes. This is why a slab is done fist for 5 days to reduce the swelling .
After that walking or pop cast is done for 6 weeks in plantigrade(90 degrees) position.
In plantar flexed ankle(120 degrees) as yours, you will have difficulty to walk in the cast, also stiffness will make it difficult to get back dorsiflexion.
Next Steps
share x-rays..
Health Tips
There is no point having a loose cast put on.
Whole point of cast is tight fit.