1) 'Social Security payment level' can be set somewhere between 0 and 120%
2) 'Social Security Index' can vary somewhere between 0 and 205.
For example, if you set the 'payment level' to 80%, then the 'index' should be about 102.
Otherwise, if your issue is the 'payment level' auto-changing, then you that may be an 'auto-control' feature that is over-riding your manual settings.
Check: country page > Automation > Automatic systems > then look at the top section of items with 'check boxes' to see if those are selected 'on'.
Even if they were all 'off', though, poor indexes/country finances/low levels of whatever the 'system' decides, can also cause 'interventions' that auto-control your country settings.