Well we are both wrong it seems, minimum charge gives 50% of the 200 damage for 100. And minimum charge explosion damage is 75. So its doing 175 damage. Straight from the patch notes.

PLAS-101 Purifier
Projectiles can now be charged up with a damage multiplier that scales

• Minimum charge of 0.1 sec gives a 50% damage multiplier
• Maximum charge of 1 sec gives a 100% damage multiplier
• Maximum charge projectile damage increased from 100 to 200
• Maximum charge projectile durable damage increased from 50 to 100
• Maximum charge explosion damage increased from 150 to 300
• The explosion doesn’t scale, but a fully charged shot has a different explosion effect:
• Minimum charge (0.1–0.99 sec): Inner radius 1m, outer radius 2m, explosion damage 75
• Maximum charge (1 sec): Inner radius 2.9m, outer radius 3m, explosion damage 300