Storage FLOAT to Compound

I'm making a code that should gradually increase the player's scale when hit by a crossbow arow. I managed to get a storage with a float value that should be the new player's scale (1.2, 1.4, 1.6 and so on), and I tried using a macro to apply it $attribute @s minecraft:generic.scale base set $(sca) and tried running it with function [macro function] with [storage entry], and got an error saying that I'm trying to use a FLOAT instead of a compound. I do not know how to turn my float into {"sca":"number"}, nor how to reference the float value in the attribute command.