I'm gonna have a go at this... let my inner sherlock have some fun...

• a single piece of "ruitspek" weighs 8g ^source
• the "share size" pack you show contains 260g (that's 32.5?! ruitspek) ^source
• I can already count almost 30 visible pieces in the jar - so you probably had two packs to fill it up

sooo... that means you had ~65 ruitspek to start the show and I'll assume you had to eat at least a hand full while making the pictures for the post to begin with...

that leads me to say:

HAY 60 MARSHMELLOWS CUADRADOS EN BRITTS JAR

I must be close!